Prostaglandins concentration

Release of oxytocin at this stage of parturition promotes prostaglandin production, particularly of the E and F series, within the decidua these prostaglandins are powerful myometrial stimulants and thus further enhance uterine contractions. The prostaglandin concentration in maternal serum and amniotic fluid increases with the progression of labor. 

Triethanolamine has been clinically tested with other model irritant compoimds for potency to stimulate signal release of proinflammatory mediators in hrnnan skin in order to find biomarkers of irritancy. Neat or aqueous triethanolamine was applied to the lower arm of 12 male volimteers after 24 h, suction blister fluid specimens were taken from the site of treated skin. Triethanolamine caused no significant increase in arachidonic acid and prostaglandin concentrations in suction blister fluid samples, in... 

Wan Y, Vinson JA, Etherton TD, Proch J, Lazarus SA, Kris-Etherton PM. 2001. Effects of cocoa powder and dark chocolate on LDL oxidative susceptibility and prostaglandin concentrations in humans. Am J Clin Nutr 74 596-602. 

No consistent effects of cannabinoids on the eyes have been reported, apart from a reduction in intraocular pressure (95). The initial reduction in intraocular pressure is followed by a rebound increase associated with increased prostaglandin concentrations. 

Cryer B, Lee E, Eeldman M. Eactors influencing gastroduodenal mucosal prostaglandin concentrations Roles of smoking and aging. Ann Intern Med 1992 116 636-640. 

The viscosity of mucus is affected by binding between calcium and the mucus, which probably arises from an ionic interaction with the sialic acid in the mucin. These variations are indicated by a change in the pH, viscoelastic properties, water, and protein content of cervical mucus. Calcium is needed to establish an intercellular contact and the assembly of tight junction in the cervical epithelium. Changes in extracellular calcium affect the permeability of tight junctions and play a role in regulating the production of cervical mucus.Prostaglandin concentrations... 

An increase in prostaglandin concentration occurs in the cat brain a few minutes following experimental fluid percussion injury (Ellis et al. 1981), and there is an associated doubling of phospholipase C activity in cerebral... 

Detailed accounts of the biosynthesis of the prostanoids have been pubUshed (14—17). Under normal circumstances arachidonic acid (AA) is the most abundant C-20 fatty acid m vivo (18—21) which accounts for the predominance of the prostanoids containing two double bonds eg, PGE2 (see Fig. 1). Prostanoids of the one and three series are biosynthesized from dihomo-S-linolenic and eicosapentaenoic acids, respectively. Concentrations ia human tissue of the one-series precursor, dihomo-S-linolenic acid, are about one-fourth those of AA (22) and the presence of PGE has been noted ia a variety of tissues (23). The biosynthesis of the two-series prostaglandins from AA is shown ia Eigure 1. These reactions make up a portion of what is known as the arachidonic acid cascade. Other Hpid products of the cascade iaclude the leukotrienes, lipoxins, and the hydroxyeicosatetraenoic acids (HETEs). Collectively, these substances are termed eicosanoids. 

Absorption spectroscopy provides an opportunity to follow concentrations of individual species with time by observing the system at more than one wavelength. An example is the dehydration of prostaglandin E methyl ester, in which the essential chemistry is shown as follows ... 

Animal cells can modify arachidonic acid and other polyunsaturated fatty acids, in processes often involving cyclization and oxygenation, to produce so-called local hormones that (1) exert their effects at very low concentrations and (2) usually act near their sites of synthesis. These substances include the prostaglandins (PG) (Figure 25.27) as well as thromboxanes (Tx), leukotrienes, and other hydroxyeicosanoic acids. Thromboxanes, discovered in blood platelets (thrombocytes), are cyclic ethers (TxBg is actually a hemiacetal see Figure 25.27) with a hydroxyl group at C-15. 

Cyclooxygenase (COX) activity is responsible for the formation of prostaglandins from their arachidonic acid precursor. Two COX isoforms have been identified, COX-1 and COX-2. While COX-1 is constitutively expressed in most tissues, COX-2 is typically only found after induction by proinflammatory stimuli. However, a constitutively expressed and highly regulated COX-2 is found in the kidney, both in the renal medulla and in the renal cortex. Renal cortical COX-2 is located in the area ofthe juxtaglomerular apparatus, and prostaglandins formed by COX-2 regulate the expression and secretion of renin in response to a reduction in NaCl concentration at the macula densa. 

A molecular variation of plasma membrane has been reported by Puccia et al. Reduction of total lipids (XL) content and significant variations of triglyceride (TG) and phospholipids (PL) fractions were observed as a consequence of exposure of C. intestinalis ovaries to TBTCl solutions. In particular, an evident TG decrease and a PL increase were observed, which probably provoked an increment in membrane fluidity, because of the high concentration of long chain fatty acids and, as a consequence, PL. This could be a cell-adaptive standing mechanism toward the pollutants, as observed in Saccharomyces cerevisiae. Also the increase in the content of the polyunsaturated fatty acids (PUPA), important in the synthesis of compounds such as prostaglandin which are present in the ovary in a stress situation, was probably a consequence of a defense mechanism to the stress provoked by the presence of TBTCl. 

Finally, other mediators such as leukotrienes and prostaglandins may also play a role. Denzlinger et al. [17] first reported an increase in urinary leukotriene E4 in anaphylactic reactions. This has been recently confirmed [18], along with an increase in 9a,l iP PGFj concentrations during anaphylaxis. 

Rats fed a purified nonlipid diet containing vitamins A and D exhibit a reduced growth rate and reproductive deficiency which may be cured by the addition of linoleic, a-linolenic, and arachidonic acids to the diet. These fatty acids are found in high concentrations in vegetable oils (Table 14-2) and in small amounts in animal carcasses. These essential fatty acids are required for prostaglandin, thromboxane, leukotriene, and lipoxin formation (see below), and they also have various other functions which are less well defined. Essential fatty acids are found in the stmctural lipids of the cell, often in the 2 position of phospholipids, and are concerned with the structural integrity of the mitochondrial membrane. 

The main problem with any study of prostaglandins (PGs) is that although brain concentrations can exceed 0.1 /rg/g, they appear to be formed on demand, rather than preformed and stored and they have very short half-lives (seconds). Also specific effective antagonists remain to be developed and PGs are widely and evenly distributed, unlike many NTs. Thus any analysis of their central effects rests heavily on either studying PG release, or their effects when applied directly (icv injection). Certainly the brain has the enzymatic ability to synthesise both prostaglandins (cycloxygenase) and leukotrienes (lypoxygenase) from arachidonic acid (AA) (see Fig. 13.8) and a number of central functions have been proposed for them (see Piomelli 1994). 

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