Directives modules

The most useful direct modulation teclmique is the current gain switching of semiconductor laser devices. This technique is unique to semiconductor sources, nearly all other lasers are modulated externally. In tliese devices tire excitation current of tire laser is modulated, resulting in modulated gain and tlierefore modulated output power. A detailed analysis of tliis process is found in [27]. Simply put, an oscillating current of tire fonn... 

Currently no drugs directly modulating the LDL receptor family are known. The possible use of drugs targeting the LDL receptor family or downstream signaling proteins may be derived from Table 1. 

Another theory for the action of stimulant diugs in ADHD involves effects on nonstiiatal monoamine systems. Frontal cortical dopamine, norepinephrine, and serotonin are clearly important in cognitive functioning and impulse control. These neurotransmitters directly modulate reward-related behaviors associated with the striatal dopamine system. Moreover, the amygdala may be pharmacologically influenced leading to enhanced... 

Besides the clear role for chemokines in modulating recruitment of cells into the CNS in HIV infection, and the potential role for chemokines to directly modulate neuronal signaling, recent evidence has suggested a link between CNS chemokine expression and enhancement of excitotoxic injury through enhancement of glutamate... 

Both methods obtain the necessary sensitivity by modulating the electrode potential between two values which define two distinct states of the electrode surface thus the chemistry to be observed is directly modulated and may be detected with great sensitivity by an appropriate form of synchronous detection. In the case of EMIRS, the modulation frequency is made sufficiently high compared to the wavelength scanning rate to enable a phase sensitive detection system to be used whereas, for SNIFTIRS, the electrode potential is held for a sufficient period at each potential to accumulate data from several interferometric scans and, after an adequate number, the two sets of data are ratioed. 

McGraw DW, Mihlbachler KA, Schwarb MR, et al. Airway smooth muscle prostaglandin-EPl receptors directly modulate beta2-adrenergic receptors within a unique heterodimeric complex. J Clin Invest 2006 116 1400-1409. 

However, recently, several other non-redox mechanisms have been implicated in the modulation of cell growth by carotenoids, which include the direct modulation of the expression of proteins and transcription factors involved in cell proliferation, differentiation and apoptosis. 

Most of the calibration methods described in the literature have been on systems using laser excitation and AOM modulation. There is much reason to believe that directly modulated LEDs are more stable however, the base of experience with LEDs is currently less. 

IFN-y also directly modulates the immune response by affecting growth, differentiation and function of both T- and B-lymphocytes. These effects are quite complex and are often influenced by additional cytokines. IFN-y acts as a growth factor in an autocrine manner for some T cell sub-populations, and it is capable of suppressing growth of other T cell types. It appears to have an inhibitory effect on development of immature B-lymphocyte populations, but it may support mature B cell survival. It can both up-regulate and down-regulate antibody production under various circumstances. 

Chen, T. Y. and Yau, K. W. Direct modulation by Ca2+-calmodulin of cyclic nucleotide-activated channel of rat olfactory receptor neurons. Nature 368 545-548,1994. 

Mature B lymphocytes express AhR and ARNT,10,12 and the ability of TCDD to suppress primary antibody responses has been known for a long time (reviewed in4). While the precise mechanisms resulting in suppression of T-dependent B cell responses in vivo have not been fully elucidated, it is clear that direct effects of TCDD on B cells plays a role. Studies using two B cell lines with differential AhR expression have linked suppression of LPS-induced IgM production to AhR activation, and have shown that AhR interactions within the 3 alpha immunoglobulin heavy chain enhancer directly influence antibody production.52-54 TCDD also appears to directly modulate the expression of CD19 on human B cells, suggesting another mechanism by which TCDD down-modulates the responsiveness of mature B cells.55... 

Another instructive example of the relevance of ambient stimuli to the nature of the effect of serotonergic manipulations on locomotor activity is provided by Brody s (27) study of PCPA. He monitored the locomotion of vehicle- and PCPA-treated rats in an open field to which the animals had been previously familiarized. Animals were tested either with or without additional stimulation in the form of flashing lights and 90 dB(A) noise bursts. Without stimulation, PCPA-treated rats were less active than controls with stimulation, PCPA-treated rats were more active. The results of these and other such studies indicate that the central serotonergic systems may not directly modulate the level of locomotor activity per se, but they may profoundly influence locomotor activity by virtue of their effects on the sensory responsivity of the animal to a wide variety of environmental stimuli. 

Figure 6-8. Incorporation of directly modulated loser diode into phase fluorometer. Reproduced from Ref. 25 with permission.

Weggen, S., Eriksen, J.L., Sagi, S.A., Pietrzik, C.U., Ozols, V., Fauq, A., Golde, T.E., and Koo, E.H., Evidence that nonsteroidal anti-inflammatory drugs decrease amyloid beta 42 production by direct modulation of gamma-secretase activity, /. Biol. Chem., 278, 31831, 2003. 

The combinatorial effects of such chemical variability of chromatin, can be used as an informational tool or to directly modulate the physical and thermodynamic constraints of this nucleoprotein assembly. In the first instance a chemical signature can be used as a targeting mechanism to allow the recognition of regulatory regions by traw -acting factors or by ATP-dependent (i.e., SWI/SNF) or... 

The notion that DNA methylation is an epigenetic mechanism that acts in conjunction with post-synthetic modifications of histones and other proteins is nowadays widely accepted and is the focus of major research effort worldwide. It must be noted though that this is probably not the only way through which methylation affects chromatin structure, and that DNA methylation may directly modulate some basic structural features of nucleosomes or the chromatin fibers they form. 

As with any metalloprotein, the chemical and physical properties of the metal ion in cytochromes are determined by the both the primary and secondary coordination spheres (58-60). The primary coordination sphere has two components, the heme macrocycle and the axial ligands, which directly affect the bound metal ion. The pyrrole nitrogen donors of the heme macrocycle that are influenced by the substitutents on the heme periphery establish the base heme properties. These properties are directly modulated by the number and type of axial ligands derived from the protein amino acids. Typical heme proteins utilize histidine, methionine, tyrosinate, and cysteinate ligands to affect five or six coordination at the metal center. 

Ray JM, Stetler-Stevenson WG. Gelatinase A activity directly modulates melanoma call adhesion and spreading. EMBO J 1995 14 908-917. 

By applying the same principle, Rotello s group also showed that dendrimer-mediated assembly of magnetic nanoparticles (-y-Fe203) can directly modulate... 

Autonomic and hormonal control of cardiovascular function. Note that two feedback loops are present the autonomic nervous system loop and the hormonal loop. The sympathetic nervous system directly influences four major variables peripheral vascular resistance, heart rate, force, and venous tone. It also directly modulates renin production (not shown). The parasympathetic nervous system directly influences heart rate. In addition to its role in stimulating aldosterone secretion, angiotensin II directly increases peripheral vascular resistance and facilitates sympathetic effects (not shown). The net feedback effect of each loop is to compensate for changes in arterial blood pressure. Thus, decreased blood pressure due to blood loss would evoke increased sympathetic outflow and renin release. Conversely, elevated pressure due to the administration of a vasoconstrictor drug would cause reduced sympathetic outflow, reduced renin release, and increased parasympathetic (vagal) outflow. 

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