Dihydrochalcones in Sweet Tea: Biosynthesis, Distribution and Neuroprotection Function.

Sweet tea is a popular herbal drink in southwest China, and it is usually made from the shoots and tender leaves of Lithocarpus litseifolius. The sweet taste is mainly attributed to its high concentration of dihydrochalcones. The distribution and biosynthesis of dihydrochaldones in sweet tea, as well as neuroprotective effects in vitro and in vivo tests, are reviewed in this paper. Dihydrochalones are mainly composed of phloretin and its glycosides, namely, trilobatin and phloridzin, and enriched in tender leaves with significant geographical specificity. Biosynthesis of the dihydrochalones follows part of the phenylpropanoid and a branch of flavonoid metabolic pathways and is regulated by expression of the genes, including phenylalanine ammonia-lyase, 4-coumarate: coenzyme A ligase, trans-cinnamic acid-4-hydroxylase and hydroxycinnamoyl-CoA double bond reductase. The dihydrochalones have been proven to exert a significant neuroprotective effect through their regulation against Aß deposition, tau protein hyperphosphorylation, oxidative stress, inflammation and apoptosis.

Conversion obstacle from Mg-protoporphyrin IX to protochlorophyllide might be responsible for chlorophyll-deficient phenotype of the Huangjinya's albino offspring.

The albino tea cultivar is one of the most important germplasms for key gene mining and high-quality tea producing. In order to elucidate the chlorophyll-deficient mechanism of albino cultivar 'Huangjinya' and its offspring, color difference, photosynthetic pigments and the relevant genes' expression of the tender shoots were comprehensively investigated in this study. Among the tested 16 offspring, 5 exhibited albino phenotype in spring and autumn, 3 showed albino phenotype in spring but normal green in autumn, while the rests were all normal green. The shoot of albino offspring had significantly higher lightness and/or yellowness than that of green ones, and possessed dramatically lower photosynthetic pigments and chlorophyll precursor protochlorophyllide (Pchlide), as well as higher chlorophyll a/chlorophyll b but lower chlorophylls/carotenoids in comparison with green ones. Among the tested genes involved in chlorophyll and carotenoid metabolism pathways, expression of the magnesium protoporphyrin IX monomethyl ester cyclase (CRD), 3,8-divinyl chlorophyllide 8-vinyl reductase (DVR), 5-aminolevulinate dehydratase 1 (HEMB1), 1-deoxy-D-xylulose 5-phosphate synthase 1 (DXS1) and 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (ISPH) was remarkably down-regulated in shoots of the albino offspring. Color difference indices of the offspring were significantly correlated with the levels of photosynthetic pigments and Pchlide, and low level of chlorophylls in shoot of albino offspring was mainly due to conversion obstacle from magnesium protoporphyrin Ⅸ (Mg-Proto IX) to Pchlide which might be attributed to down-regulatory expression of CRD and DVR.

Acrylamide biodegradation ability and plant growth-promoting properties of Variovorax boronicumulans CGMCC 4969.

Species of the genus Variovorax are often isolated from nitrile or amide-containing organic compound-contaminated soil. However, there have been few biological characterizations of Variovorax and their contaminant-degrading enzymes. Previously, we reported a new soil isolate, Variovorax boronicumulans CGMCC 4969, and its nitrile hydratase that transforms the neonicotinoid insecticide thiacloprid into an amide metabolite. In this study, we showed that CGMCC 4969 is able to degrade acrylamide, a neurotoxicant and carcinogen in animals, during cell growth in a mineral salt medium as well as in its resting state. Resting cells rapidly hydrolyzed 600 mg/L acrylamide to acrylic acid with a half-life of 2.5 min. In in vitro tests, CGMCC 4969 showed plant growth-promoting properties; it produced a siderophore, ammonia, hydrogen cyanide, and the phytohormone salicylic acid. Interestingly, in soil inoculated with this strain, 200 mg/L acrylamide was completely degraded in 4 days. Gene cloning and overexpression in the Escherichia coli strain Rosetta (DE3) pLysS resulted in the production of an aliphatic amidase of 345 amino acids that hydrolyzed acrylamide into acrylic acid. The amidase contained a conserved catalytic triad, Glu59, Lys 134, and Cys166, and an "MRHGDISSS" amino acid sequence at the N-terminal region. Variovorax boronicumulans CGMCC 4969, which is able to use acrylamide for cell growth and rapidly degrade acrylamide in soil, shows promising plant growth-promoting properties. As such, it has the potential to be developed into an effective Bioaugmentation strategy to promote growth of field crops in acrylamide-contaminated soil.

The latitudinal and longitudinal allelopathic patterns of an invasive alligator weed (Alternanthera philoxeroides) in China.

Allelopathy has been considered a good explanation for the successful invasion of some invasive plants. However, the real latitudinal and longitudinal allelopathic effects on native species have rarely been documented since many exotics have spread widely. We conducted a Petri dish experiment to determine the latitudinal and longitudinal allelopathic patterns of an invasive alligator weed (Alternanthera philoxeroides) on a common crop (Lactuca sativa) in China, and find what determines the allelopathic intensity. The results showed that the allelopathic effects of A. philoxeroides increased with the latitude while decreased with the longitude. This indicated that A. philoxeroides used its allelopathy to gain competitive advantages more in its recent invaded communities than that in its early invaded ones as A. philoxeroides is expanding from southeast China to northwest China. Furthermore, we found that the allelopathic intensity of A. philoxeroide was negatively correlated to the leaf contents of soluble carbohydrate (SC), carbon (C) and nitrogen (N), but that was positively correlated to the leaf contents of soluble protein (SP), free amino acids (FAA), plant polyphenol (PP), phosphorus (P) and potassium (K). These results suggested that the allelopathic intensity of A. philoxeroide was more determined by the limited P and K nutrients as well as the intermediate allelochemicals (SP, FAA, PP) rather than the unlimited C, N and SC. Thus, we can speculate that the negative or positive effects of plant aqueous extracts are a function of not only the extract concentrations but also the trade-offs between inhibition and promotion of all components in the extracts. Then we could reduce the allelopathic effects of A. philoxeroide by controlling the component contents in the plant tissues, by fertilization or other managements, especially in the plant recent invaded communities.

Advances in electrical impedance tomography-based brain imaging.

Novel advances in the field of brain imaging have enabled the unprecedented clinical application of various imaging modalities to facilitate disease diagnosis and treatment. Electrical impedance tomography (EIT) is a functional imaging technique that measures the transfer impedances between electrodes on the body surface to estimate the spatial distribution of electrical properties of tissues. EIT offers many advantages over other neuroimaging technologies, which has led to its potential clinical use. This qualitative review provides an overview of the basic principles, algorithms, and system composition of EIT. Recent advances in the field of EIT are discussed in the context of epilepsy, stroke, brain injuries and edema, and other brain diseases. Further, we summarize factors limiting the development of brain EIT and highlight prospects for the field. In epilepsy imaging, there have been advances in EIT imaging depth, from cortical to subcortical regions. In stroke research, a bedside EIT stroke monitoring system has been developed for clinical practice, and data support the role of EIT in multi-modal imaging for diagnosing stroke. Additionally, EIT has been applied to monitor the changes in brain water content associated with cerebral edema, enabling the early identification of brain edema and the evaluation of mannitol dehydration. However, anatomically realistic geometry, inhomogeneity, cranium completeness, anisotropy and skull type, etc., must be considered to improve the accuracy of EIT modeling. Thus, the further establishment of EIT as a mature and routine diagnostic technique will necessitate the accumulation of more supporting evidence.

Nonlinear optical properties of near-infrared region Ag2S quantum dots pumped by nanosecond laser pulses.

This study investigates near-infrared region Ag2S quantum dots (QDs) and their nonlinear optical response under 532 nm nanosecond laser pulses. Our experimental result shows that nonlinear transmission is reduced from 0.084 to 0.04. The observed narrowing behavior of the output pulse width shows superior optical limiting. We discuss the physical mechanisms responsible for the nonlinear optical response of the QDs. The average size of the nanocrystals was 5.5 nm. Our results suggest the possibility of using these Ag2S QDs for photoelectric, biosensor, optical ranging, and self-adaptive technologies.

Optimizing the synthesis of CdS/ZnS core/shell semiconductor nanocrystals for bioimaging applications.

In this study, we report on CdS/ZnS nanocrystals as a luminescence probe for bioimaging applications. CdS nanocrystals capped with a ZnS shell had enhanced luminescence intensity, stronger stability and exhibited a longer lifetime compared to uncapped CdS. The CdS/ZnS nanocrystals were stabilized in Pluronic F127 block copolymer micelles, offering an optically and colloidally stable contrast agents for in vitro and in vivo imaging. Photostability test exhibited that the ZnS protective shell not only enhances the brightness of the QDs but also improves their stability in a biological environment. An in-vivo imaging study showed that F127-CdS/ZnS micelles had strong luminescence. These results suggest that these nanoparticles have significant advantages for bioimaging applications and may offer a new direction for the early detection of cancer in humans.

Identification of a novel germline missense mutation of the androgen receptor in African American men with familial prostate cancer.

Race, family history and age are the unequivocally accepted risk factors for prostate cancer (PCa). Androgen receptor (AR)-dependent signaling is an important element in prostate carcinogenesis and its progression to metastatic disease. We examined the possibility of genomic changes in the AR in association with familial PCa in African Americans who have a higher incidence and mortality rate and a clinically more aggressive disease presentation than Caucasians. Genomic DNAs of 60 patients from 30 high-risk African American and Caucasian families participating in the Louisiana State University Health Sciences Center genetic linkage study of PCa were studied. Exon-specific polymerase-chain reaction, bi-directional automated sequencing and restriction enzyme genotyping were used to analyze for mutations in the coding region of the AR gene. We identified a germline AR (A1675T) (T559S) substitution mutation in the DNA-binding domain in three PCa-affected members of an African-American family with a history of early-onset disease. The present study describes the first AR germline mutation in an African-American family with a history of familial PCa. The AR (T559S) mutation may contribute to the disease by altering AR DNA-binding affinity and/or its response to androgens, non-androgenic steroids or anti-androgens. Additional studies will be required to define the frequency and contribution of the AR (A1675T) allele to early-onset and/or familial PCa in African Americans.

[Soluble expression and characterization of disulfide bond-rich subdomains of membrane protein p185 in Escherichia coli].

Transmembrane protein p185 (the product of Her2/c-erbB-2 gene) is a member of the epidermal growth factor receptor (EGFR) family. Its overexpression was found in about 30% of breast cancer. It is essential to obtain soluble extracellular domain (ECD) of p185, especially disulfide bond rich domains, for identifying the epitopes of anti-p185 antibodies and researching the interrelationship between the antigen and antibody. The disulfide bond rich domain I-II and domain IV of p185 ECD were amplified from plasmid pBabe/erbB-2 by PCR respectively. These two fragments were inserted into pGEX/4T-1 vector, transfected into E. coli Origami B (DE3) pLysS and expressed inductively by low concentration of IPTG and low temperature overnight. After the pressure lysis of cells, the supernatants were analyzed by SDS-PAGE and the result demonstrated that this GST-fusion protein was expressed solubly in the amount of 10-15 mg/L. By the ELISA, Western blot and other immunological assays, the fusion proteins and their GST cut-off derivates both showed binding activities with several anti-p185 antibodies respectively. These results indicated that it was a feasible and effectual method to express disulfide bond rich domain I-II and domain IV of p185 ECD and this method may also be used to express other disulfide bond rich proteins.