Attenuation mechanisms

Brookman, G.T., Flanagan, M., Kebe, J.O. (1985) Literature Survey Hydrocarbon Solubilities and Attenuation Mechanisms, prepared for Environmental Affairs Dept, of American Petroleum Institute. API Publication No. 4414, August, 1985, Washington D.C. 

Dusting Powders are sprinkled onto the intact skin and consist of talc, magnesium stearate, silicon dioxide (silica), or starch. They adhere to the skin, forming a low-friction film that attenuates mechanical irritation. Powders exert a drying (evaporative) effect. 

The decoy function of aberrant and intact sFas was discussed above now we will review the attenuating mechanism of aberrant mFas for Fas-mediated apoptosis. Data from our ATL studies and the literature indicate several different mechanisms for attenuating Fas-mediated signaling depending on the aberrant structure of the Fas molecule produced by the mutated Fas gene, as shown in Fig. 8. 

However, as pH drops, the ability of natural attenuation mechanisms in the ash (e.g., carbona-tion, sorption to hydrous ferric oxides) becomes more dominant and leaching is reduced. 

Quartaroli, M., Fasdelli, N., Bettelini, L., Maraia, G., Corsi, M. GV196771A, an NMDA receptor/glycine site antagonist, attenuates mechanical allodynia in neuropathic rats and reduces tolerance induced by morphine in mice, Eur. J. Pharmacol. 2001, 430, 219-227. 

Sutton, J.L., Maccecchini, M.L., Kajander, K.C. The kainate receptor antagonist 2S,4R-4-methylglutamate attenuates mechanical allodynia and thermal hyperalgesia in a rat model of nerve injury, Neuroscience 1999, 91, 283-292. 

The trp operon attenuation mechanism uses signals encoded in four sequences within a 162 nucleotide leader region at the 5 end of the mRNA, preceding the initiation codon of the first gene (Fig. 28-21a). Within the leader lies a region known as the attenuator, made up of sequences 3 and 4. These sequences base-pair to... 

Yanofsky, C., Konan, K.V., Sarsero, J.P. (1996) Some novel transcription attenuation mechanisms used by bacteria. Biochimie... 

This attenuator mechanism of control is amazingly simple because it requires no proteins other than those normally used for transcription and translation. One might expect such a simple and effective mechanism to be used repeatedly for other operons involved in amino acid biosynthesis. Indeed, for several other amino acid biosynthetic pathways in E. coli for which tRNA charging is involved in regulation, attenuator mechanisms have been found. 

Yamamoto T., Nozaki-Taguchi N., and Sakashita Y. (2001). Spinal N-acetyl-alpha-linked acidic dipeptidase (NAALADase) inhibition attenuates mechanical allodynia induced by paw carrageenan injection in the rat. Brain Res. 909 138-144. 

In the next table, one can see how far away a person has to be from an SRV vent if noise is to be below, say, 130 or 115dB(A). The table is for spherical radiation but includes no other attenuation mechanisms. This table, expressed in metres, can be used to provide a first estimate of the vertical length of vent pipe that is required where stack height is to be used as the main method of noise reduction. 

Fig. 1. (—)-Iinalool attenuates mechanical allodynia induced by spinal nerve ligation in mice. (A and B) Mechanical allodynia developed and maintained over time following spinal nerve ligation (SNL). (A) A single dose of linalool (100 mg/kg s.c.) did not cause any significant changes compared to SNL and vehicle-treated animals. (B) Linalool administered daily for 7 days attenuated mechanical allodynia compared to SNL animals and SNL animals treated with the vehicle ( p < 0.001 vs vehicle ANOVA+Tukey test). Data are expressed as mean SEM of the value corresponding to 50% of pain threshold and are normalized to the basal value of each animal. Differences are evaluated using oneway analysis of variance (ANOVA), followed by post hoc Tukey multiple comparison tests, p < 0.05 was regarded as significant.

It has been demonstrated that neuropathic pain is opioid resistant and, indeed, neither systemic nor i.t. administration of opioids reduced effectively neuropathic pain in rats (Bian et al., 1995 Lee et al., 1995 Mao et al., 1995 Ossipov et al., 1995). It seems worth to note that s.c. administration of (—) linalool attenuates mechanical allodynia in spinal nerve ligation model of neuropathic pain in mice (Levato et al., 2006). 

Hydrolysis results in products, such as alcohols and alkenes, which may be more susceptible to biodegradation - hence hydrolysis may be a significant natural attenuation mechanism. 

Acoustic-absorbing material measurement of acoustic properties, 248 selection for underwater application, 248 Acoustic attenuation mechanisms mode conversion, 182-187 redirection of sound, 182 scattering of sound, 185-194... 

Figure 1 Generalized model for sensing regulatory effectors by nascent mRNA leader transcripts. Transcription attenuation mechanisms have been identified in which the nascent transcript interacts with a translating 70S ribosome, a protein, an RNA molecule or a small metabolite, (a) Binding of the effector molecule promotes transcription termination, (b) Binding of the effector molecule promotes transcription readthrough (antitermination). See text for details.

TrpR, which is a DNA binding repressor protein, regulates transcription initiation of the E. coli trpEDCBA operon. Under tryptophan limiting conditions, TrpR represses transcription initiation, whereas repression is relieved in the presence of excess tryptophan. Once transcription initiates the elongating transcription complex is subject to control by transcription attenuation (reviewed in References 5 and 6). The leader transcript can form three RNA secondary structures that are referred to as the pause hairpin, the antiterminator structure, and an intrinsic terminator hairpin. Because the antiterminator shares nucleotides in common with the terminator, their formation is mutually exclusive. The pause hairpin has two additional roles in this transcription attenuation mechanism it serves as an anti-antiterminator stmc-ture that prevents antiterminator formation, and it codes for a leader peptide. A model of the E. coli trp operon transcription attenuation mechanism is presented in Fig. 2a. 

The most recently identified class of transcription attenuation mechanism involves direct sensing of the effector molecule by the nascent transcript (52-54). These RNA sensors control metabolically diverse pathways. As for the other attenuation and antitermination mechaiusms discussed thus far, recognition of the particular effector molecule occurs with the appropriate affinity and high specificity required for precise control of gene expression. 

Yakhnin AV, Babitzke P. NusA-stimulated RNA polymerase pausing and termination participates in the Bacillus subtilis trp operon attenuation mechanism in vitro. Proc. Natl. Acad. Sci. U.S.A. 2002 99 11067-11072. 

Sudershana S, Du H, Mahalanabis M, Babitzke P. A 5 RNA stem-loop participates in the transcription attenuation mechanism that controls expression of the Bacillus subtilis trpEDCFBA operon. J. Bacteriol. 1999 181 5742-5750. 

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