Adaptive evolution of MRGX2, a human sensory neuron specific gene involved in nociception

MRGX2, a G-protein-coupled receptor, is specifically expressed in the sensory neurons of the human peripheral nervous system and involved in nociception. Here, we studied DNA polymorphism patterns and evolution of the MRGX2 gene in world-wide human populations and the representative nonhuman primate species. Our results demonstrated that MRGX2 had undergone adaptive changes in the path of human evolution, which were likely caused by Darwinian positive selection. The patterns of DNA sequence polymorphisms in human populations showed an excess of derived substitutions, which against the expectation of neutral evolution, implying that the adaptive evolution of MRGX2 in humans was a relatively recent event. The reconstructed secondary structure of the human MRGX2 revealed that three of the four human-specific amino acid substitutions were located in the extra-cellular domains. Such critical substitutions may alter the interactions between MRGX2 protein and its ligand, thus, potentially led to adaptive changes of the pain-perception-related nervous system during human evolution. (c) 2005 Elsevier B.V. All rights reserved.

The dynamics of hippocampal sensory gating during the development of morphine dependence and withdrawal in rats

The effects of morphine on hippocampal sensory gating (N40) during the development of morphine dependence and withdrawal were investigated in the double click auditory evoked potential (EP) suppression paradigm. Rats were made dependent upon morphine hydrochloride by a series of injections (every 12h) over 6 days, followed by withdrawal after stopping morphine administration. Hippocampal gating was examined during the development of dependence and withdrawal. Moreover, the DA antagonist haloperidol was used to assess the contribution of dopamine to hippocampal gating induced by morphine. Our results showed that the morphine-treated rats exhibited significantly disrupted hippocampal gating during the development of morphine dependence and this disrupted gating was partially reversed by haloperidol pretreatment. In contrast, there was significantly enhanced hippocampal gating at the fifth and sixth days of withdrawal. The dynamics of hippocampal gating during the development of morphine dependence and withdrawal suggests the interaction between the hippocampus and opioids. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

Influence of physical parameters of sound on the sensory gating effects of N40 in rats

Sensory gating is the ability of the brain to modulate its sensitivity to incoming stimuli. The N40 component of the auditory evoked potential, evaluated with the paired click paradigm, was used to probe the gating effect in rats. The physical characteris

MEASUREMENT AND SIMULATION OF THE TURN-ON DELAY TIME JITTER IN GAIN-SWITCHED SEMICONDUCTOR-LASERS

The turn-on delay time jitter of four different unbiased gain-switched laser types is determined by measuring the temporal probability distribution of the leading edge of the emitted optical pulse. One single-mode 1.5-mu-m distributed feed-back laser and three multimode Fabry-Perot lasers emitting at 750 nm and 1.3-mu-m are investigated. The jitter is found to decrease for all lasers with increasing injection current. For multimode lasers it decreases from 8 ps excited slightly above threshold down to below 2 ps at three times the threshold current. The jitter of the distributed feedback (DFB) laser is a factor of 3-5 larger than the jitter of the three multimode lasers. A new model to predict the turn-on delay time jitter is presented and explains the experiments quantitatively.

Defensive and Sensory Chemical Ecology of Brown Algae

The ecological interaction of brown algae are important as these macroalgae are common and often keystone members in many benthic marine communities.This review highlights their chemical interactions,particularly with potential herbivores,but also with fouling oranganisms,with potential pathogens,with each other as gametes,and with their microenvironments when they are spores.Phlorotannins,which are phenolic compounds unique to brown algae,have been studied hesvily in many of these respects and sre highlightes here.This includes recent controversy about their roles as defences against herbivory,as well as new understanding of their roles in primary cellular functions that may,in many instances,be more important than ,and which at least have to be considered in convert with,any possible ecological functions.Brown algae have also been useful models for testing theoties about the evolution of and ecological constraints on chemical defence.Furthermore,their mocroscopic motile gametes and spores have the ability to react to their chemical environments behavirourally.

Sensitive turn-on fluorescent detection of cyanide based on the dissolution of fluorophore functionalized gold nanoparticles

We report a simple fluorescent method for sensitive cyanide detection based on the dissolution of Rhodamine B-adsorbed gold nanoparticles by cyanide.

Turn-on fluorescent cyanide sensor based on copper ion-modified CdTe quantum dots

A new fluorescent sensor for the sensitive and selective detection of cyanide (CN-) in aqueous media was developed herein. The sensing approach is based on CN--modulated quenching behavior of Cu2+ toward the photoluminescence (PL) of CdTe quantum dots (QDs). In the presence of CN-, the PL of QDs that have been quenched by Cu2+ was found to be efficiently recovered, which then allows the detection of CN- in a very simple approach. Experimental results showed that the pH of the buffer solution, concentration of copper ions, and size of CdTe QDs all influenced the response of the sensor to CN-. Under the optimal conditions, a good linear relationship between the PL intensity and the concentration of CN- can be obtained in the range of 3.0 x 10(-7) to 1.2 x 10(-5) M, with a detection limit as low as 1.5 x 10(-7) M. In addition, the present fluorescent sensor possesses remarkable selectivity for cyanide over other anions, and negligible influences were observed on the cyanide detection by the coexistence of other anions or biological species (such as albumin and typical blood constituents).

Turn-on fluorescent detection of cyanide based on the inner filter effect of silver nanoparticles

A simple, sensitive fluorescent method for detecting cyanide has been developed based on the inner filter effect (IFE) of silver nanoparticles (Ag NPs). With a high extinction coefficient and tunable plasmon absorption feature, Ag NPs are expected to be a powerful absorber to tune the emission of the fluorophore in the IFE-based fluorescent assays. In the present work, we developed a turn-on fluorescent assay for cyanide based on the strong absorption of Ag NPs to both excitation and emission light of an isolated fluorescence indicator. In the presence of cyanide, the absorber Ag NPs will dissolve gradually, which then leads to recovery of the IFE-decreased emission of the fluorophore. The concentration of Ag NPs in the detection system was found to affect the fluorescence response toward cyanide greatly. Under the optimum conditions, the present IFE-based approach can detect cyanide ranging from 5.0 x 10 (7) to 6.0 x 10 (4) M with a detection limit of 2.5 x 10 (7) M, which is much lower than the corresponding absorbance-based approach and compares favorably with other reported fluorescent methods.