Signal Amplification Effect Research Articles

Development of Precise Pharmocodiagnostic (PharmDx) Tests for Molecular Targeted Therapies

Advanced biomolecular technologies have begun to provide beneficial means to detect a variety of cellular molecules for tumor diagnosis, as well as predictive and prognostic factors of cancers. This new understanding of the molecular basis of cancers has led to the development of molecular targeted approaches to cancer prevention and treatment. Molecules involved in the growth factor signaling system have become favored targets for molecular targeted therapies in translational research and clinical development. The current molecular targeting agents are classified into humanized or camera monoclonal antibodies and small-molecule tyrosine kinase inhibitors. Patients with HER2-overexpressing, metastatic breast cancer are beginning to benefit from the first commercially humanized monoclonal antibody (Herceptin), and the first small-molecule tyrosine kinase inhibitor (Gleevec/Glivec) has been introduced in Japan. Gleevec/Glivec has been demonstrated to have a long-term clinical benefit for most refractory patients with Philadelphia chromosome-positive chronic myelogenous leukemia as well as with KIT-expressing, unresectable and/or metastatic gastrointestinal stromal tumor. Accurate and reliable HER2 or KIT testing is performed to determine patient eligibility for Herceptin or Gleevec/Glivec therapy, respectively. HER1 (EGFR) and HER2 are the most widely studied target molecules for therapeutic inhibitions. HER family targeting has been initiated as the basis of extensive and growing drug development programs in various companies. A key technology of targeted therapies is molecular diagnosis with target identification. Along with the progressive development of HER-targeted therapies, the need to standardize immunohistochemical diagnostic tests for each targeted therapy is ever more pressing. Although the standardization of immunohistochemistry using archival formalin-fixed specimens is a tremendous challenge that will require great effort and considerable research, the development of an ideal pharmDx test for target molecular identification will be achieved by the optimal combination of heat-induced antigen retrieval with calcium-chelating solutions, effective signal amplification, and automated staining approaches. The expression levels and phosphorylation/activation of various signaling molecules will be valuable in defining subpopulations of patients who may potentially respond to molecular targeted therapies.

Spectrophotometric enzymatic cycling method using l-glutamate dehydrogenase and d-phenylglycine aminotransferase for determination of l-glutamate in foods

This report describes a new spectrophotometric method capable of determining low levels of l-glutamate. The assay is based on substrate cycling between l-glutamate dehydrogenase (GlDH) and the novel enzyme d-phenylglycine aminotransferase ( d-PhgAT). In this system, GlDH converts l-glutamate to 2-oxoglutarate with concomitant reduction of NAD + to NADH. The 2-oxoglutarate is recycled to l-glutamate in a transamination reaction catalyzed by d-PhgAT using d-4-hydroxyphenylglycine as an amino donor, which is converted to 4-hydroxybenzoylformate. Both NADH and 4-hydroxybenzoylformate strongly absorb UV light at 340 nm ( ε 340 nm =6.22×10 3 and 8.90×10 3 l mol −1 cm −1, respectively). The signal amplification effect of the cycling reactions is thus further enhanced by the combined absorption of the two accumulating reaction products. The standard calibration curve for l-glutamate was linear from 0.2 to 20 μM, with a detection limit of 0.14 μM. Food samples can be significantly diluted before subjected to the assay, thus reducing the effects of interfering substances. Because of the unique substrate specificity of d-PhgAT, l-glutamate could be selectively determined in the presence of other common amino acids at relatively high concentrations. The assay was satisfactorily applied to measure l-glutamate in various kinds of food products. The procedure is simple, rapid, accurate, and should be easily automated.

Identification of a Region within the ErbB2/HER2 Intracellular Domain That Is Necessary for Ligand-independent Association

Ligand-independent ErbB2 activation occurs principally by two distinct mechanisms: overexpression and mutation. Overexpression of ErbB2 at the plasma membrane drives receptor self-association in a concentration-dependent manner, which in turn leads to constitutive receptor activation. Subsets of human breast cancers contain a molecular alteration that leads to erbB2 gene amplification and subsequent protein overexpression. Although not recognized to occur in human cancers, mutation can also lead to increased ErbB2 association. A well characterized mutant of the rodent ortholog neu involves substitution of glutamate for valine within the transmembrane domain. In each case, a number of explanations have been proposed to explain the resulting ErbB2 activation. These include stabilization of receptor oligomers, release of negative constraints, and altered receptor conformations. Here we define a short amino acid segment comprising amino acids 966-968 in the intracellular domain that seemingly disrupts receptor-receptor association that is driven either by overexpression or mutation in the transmembrane region. Because of the hydrophobic nature of these amino acids (VVI), we propose that alteration of this segment likely results in a global conformational change in an area that has been proposed previously to be a dimerization motif for ErbB homomeric association.

Phase reversal of vibratory signals in honeycomb may assist dancing honeybees to attract their audience.

Forager honeybees dancing on the comb are able to attract dance-followers from distances across the comb that are too remote for tactile or visual signals to play a role. An alternative signal could be the vibrations of the comb at 200-300 Hz generated by dancing bees but which, without amplification, may not be large enough to alert remote dance-followers. We describe here, however, an unexpected property of honeycomb when it is subjected to vibration at around 200 Hz that would represent an effective amplification of the vibratory signals for remote dance-followers. We find that, at a specific distance from the origin of an imposed vibration, the walls across a single comb cell abruptly reverse the phase of their displacement and move in opposite directions to one another. Behavioural measurements show that the distance from which the majority of remote dance-followers are recruited coincides with the location of this phase-reversal phenomenon relative to the signal source. We propose that effective signal amplification by the phase-reversal phenomenon occurs when bees straddle a cell across which the phase reversal is expressed. Such a bee would be subjected to a situation in which the legs were moving towards and away from one another instead of in the same direction. In this manner, remote dance-followers could be alerted to a dancer performing in their vicinity.

Electrochemical biosensor based on supported planar lipid bilayers for fast detection of pathogenic bacteria

This paper presents a new ion-channel biosensor based on supported bilayer lipid membrane for direct and fast detection of Campylobacter species. The sensing element of a biosensor is composed of a stainless-steel working electrode, which is covered by artificial bilayer lipid membrane (BLM). Antibodies to bacteria embedded into the BLM are used as channel forming proteins. The biosensor has a strong signal amplification effect, which is defined as the total number of ions transported across the BLM. The total number of (univalent) ions flowing through the channels is 10 10 ions s −1. The biosensor showed a very good sensitivity and selectivity to Campylobacter species.

Nonlinear interaction of an electromagnetic wave and a dc current in a metallic film

The nonlinear interaction of a dc current flowing in a thin metal film with an electromagnetic wave illuminating the sample in a symmetric manner with respect to the magnetic field is investigated theoretically. The nonlinearity is due to the most typical mechanism for pure metals at low temperatures — the magnetodynamic mechanism, involving the effect of the magnetic field of the current and wave field on the electron trajectories. It is shown that this interaction leads to sharp kinks in the time dependence of the electric field of the wave at the surface of the sample and to a peculiar electromagnetic signal amplification effect.

Signal transduction in bacteria: phospho-neural network(s) inEscherichia coli?

The molecular basis of many forms of signal transfer in living organisms is provided via the transient phosphorylation of regulatory proteins by transfer of phosphoryl groups between these proteins. The dominant form of signal transduction in prokaryotic microorganisms proceeds via so-called two-component regulatory systems. These systems constitute phosphoryl transfer pathways, consisting of two or more components. Most of these pathways are linear, but some converge and some are divergent. The molecular properties of some of the well-characterised representatives of two-component systems comply with the requirements to be put upon the elements of a neural network: they function as logical operators and show the phenomenon of autoamplification. Because there are many phosphoryl transfer pathways in parallel and because there also appears to be cross-talk between these pathways, the total of all two-component regulatory systems in a single prokaryotic cell may show the typical characteristics of a 'phospho-neural network'. This may well lead to signal amplification, associative responses and memory effects, characteristics which are typical for neural networks. One of the main challenges in molecular microbial physiology is to determine the extent of the connectivity of the constituting elements of this presumed 'phospho-neural network', and to outline the extent of intelligence-like behaviour this network can generate. Escherichia coli is the organism of choice for this characterization.

Silicon phototransistor vidicon

The use of silicon phototransistor arrays as high gain targets in vidicon camera tubes is shown to provide a sensitivity advantage. An analysis of device operating parameters indicates that signal enhancement can be obtained during both the write and read portions of an array element's duty cycle. Maximum effective signal amplification is secured by choosing a design which recharges the collector-base storage capacitance mostly during the read interval. Expressions for the effective signal gain in terms of transistor common base current gains and elemental capacitances have been derived, and the effects of phototransistor operation on vidicon sensitivity, image persistence, and dynamic range have been considered. Experimental transistor arrays have been fabricated and have been used for the first successful demonstration of phototransistor signal gain under the usual conditions of vidicon operation. Signal gains exceeding 70 have been recorded.