Characterization of binding of leukotriene C4 by human multidrug resistance protein 1: evidence of differential interactions with NH2- and COOH-proximal halves of the protein

Multidrug resistance protein 1 (MRP1) is capable of actively transporting a wide range of conjugated and unconjugated organic anions. The protein can also transport additional conjugated and unconjugated compounds in a GSH- or S-methyl GSH-stimulated manner. How MRP1 binds and transports such structurally diverse substrates is not known. We have used [(3)H]leukotriene C(4) (LTC(4)), a high affinity glutathione-conjugated physiological substrate, to photolabel intact MRP1, as well as fragments of the protein expressed in insect cells. These studies revealed that: (i) LTC(4) labels sites in the NH(2)- and COOH-proximal halves of MRP1, (ii) labeling of the NH(2)-half of MRP1 is localized to a region encompassing membrane-spanning domain (MSD) 2 and nucleotide binding domain (NBD) 1, (iii) labeling of this region is dependent on the presence of all or part of the cytoplasmic loop (CL3) linking MSD1 and MSD2, but not on the presence of MSD1, (iv) labeling of the NH(2)-proximal site is preferentially inhibited by S-methyl GSH, (v) labeling of the COOH-proximal half of the protein occurs in a region encompassing transmembrane helices 14-17 and appears not to require NBD2 or the cytoplasmic COOH-terminal region of the protein, (vi) labeling of intact MRP1 by LTC(4) is strongly attenuated in the presence of ATP and vanadate, and this decrease in labeling is attributable to a marked reduction in LTC(4) binding to the NH(2)-proximal site, and (vii) the attenuation of LTC(4) binding to the NH(2)-proximal site is a consequence of ATP hydrolysis and trapping of Vi-ADP exclusively at NBD2. These data suggest that MRP1-mediated transport involves a conformational change, driven by ATP hydrolysis at NBD2, that alters the affinity with which LTC(4) binds to one of two sites composed, at least in part, of elements in the NH(2)-proximal half of the protein.     

Microsatellite mapping of a Triticum urartu Tum. derived powdery mildew resistance gene transferred to common wheat (Triticum aestivum L.)

A powdery mildew resistance gene from Triticum urartu Tum. accession UR206 was successfully transferred into hexaploid wheat (Triticum aestivum L.) through crossing and backcrossing. The F₁ plants, which had 28 chromosomes and an average of 5.32 bivalents and 17.36 univalents in meiotic pollen mother cells (PMC), were obtained through embryos rescued owing to shriveling of endosperm in hybrid seed of cross Chinese Spring (CS) × UR206. Hybrid seeds were produced through backcrossing F₁ with common wheat parents. The derivative lines had normal chromosome numbers and powdery mildew resistance similar to the donor UR206, indicating that the powdery mildew resistance gene originating from T. urartu accession UR206 was successfully transferred and expressed in a hexaploid wheat background. Genetic analysis indicated that a single dominant gene controlled the powdery mildew resistance at the seedling stage. To map and tag the powdery mildew resistance gene, 143 F₂ individuals derived from a cross UR206 × UR203 were used to construct a linkage map. The resistant gene was mapped on the chromosome 7AL based on the mapped microsatellite makers. The map spanned 52.1 cM and the order of these microsatellite loci agreed well with the established microsatellite map of chromosome arm 7AL. The resistance gene was flanked by the microsatellite loci Xwmc273 and Xpsp3003, with the genetic distances of 2.2 cM and 3.8 cM, respectively. On the basis of the origin and chromosomal location of the gene, it was temporarily designated PmU.     

Interpreting expression profiles of cancers by genome-wide survey of breadth of expression in normal tissues

A critical and difficult part of studying cancer with DNA microarrays is data interpretation. Besides the need for data analysis algorithms, integration of additional information about genes might be useful. We performed genome-wide expression profiling of 36 types of normal human tissues and identified 2503 tissue-specific genes. We then systematically studied the expression of these genes in cancers by reanalyzing a large collection of published DNA microarray datasets. We observed that the expression level of liver-specific genes in hepatocellular carcinoma (HCC) correlates with the clinically defined degree of tumor differentiation. Through unsupervised clustering of tissue-specific genes differentially expressed in tumors, we extracted expression patterns that are characteristic of individual cell types, uncovering differences in cell lineage among tumor subtypes. We were able to detect the expression signature of hepatocytes in HCC, neuron cells in medulloblastoma, glia cells in glioma, basal and luminal epithelial cells in breast tumors, and various cell types in lung cancer samples. We also demonstrated that tissue-specific expression signatures are useful in locating the origin of metastatic tumors. Our study shows that integration of each gene's breadth of expression (BOE) in normal tissues is important for biological interpretation of the expression profiles of cancers in terms of tumor differentiation, cell lineage, and metastasis.     

Programmable mechanical stimulation influences tendon homeostasis in a bioreactor system

Identification of functional programmable mechanical stimulation (PMS) on tendon not only provides the insight of the tendon homeostasis under physical/pathological condition, but also guides a better engineering strategy for tendon regeneration. The aims of the study are to design a bioreactor system with PMS to mimic the in vivo loading conditions, and to define the impact of different cyclic tensile strain on tendon. Rabbit Achilles tendons were loaded in the bioreactor with/without cyclic tensile loading (0.25 Hz for 8 h/day, 0–9% for 6 days). Tendons without loading lost its structure integrity as evidenced by disorientated collagen fiber, increased type III collagen expression, and increased cell apoptosis. Tendons with 3% of cyclic tensile loading had moderate matrix deterioration and elevated expression levels of MMP‐1, 3, and 12, whilst exceeded loading regime of 9% caused massive rupture of collagen bundle. However, 6% of cyclic tensile strain was able to maintain the structural integrity and cellular function. Our data indicated that an optimal PMS is required to maintain the tendon homeostasis and there is only a narrow range of tensile strain that can induce the anabolic action. The clinical impact of this study is that optimized eccentric training program is needed to achieve maximum beneficial effects on chronic tendinopathy management. Biotechnol. Bioeng. 2013; 110: 1495–1507. © 2012 Wiley Periodicals, Inc.     

Sunfleck limits the small-scale distribution of endangered <Emphasis Type="Italic">Kingdonia uniflora</Emphasis> in the natural habitat of subalpine forest proved by its photosynthesis

The physiological effects of sunflecks on understory plants are poorly understood. Kingdonia uniflora is an endemic and endangered species in China, with a patchy distribution over much of its range. Sunflecks are reportedly the likely dominant factor in determining its patchy distribution. We studied the photosynthesis of K. uniflora in the field to test whether understory sunflecks result in photoinhibition and, thereby, potentially influence its patchy distribution. K. uniflora exhibited the low dark respiration rates, low light compensation points, and low light saturation points characteristic of shade-tolerant plants, allowing maintenance during the long periods of low understory light. Moreover, K. uniflora was able to regulate light energy utilization by non-photochemical quenching in low light. Gas exchange parameters were measured in six treatments (sunfleck-enriched, sunfleck-enriched with added saturation light, sunfleck-enriched with filtered ultraviolet-B (UV-B) radiation , sunfleck-limited, sunfleck-limited with added saturation light, and sunfleck-limited with filtered UV-B). The sunfleck-enriched treatment caused photoinhibition in K. uniflora, in part due to a UV-B-induced decrease in Pn. In addition, the application of simulated sunflecks indicated that K. uniflora leaves do not need continuous light. The photosynthetic responses of K. uniflora to sunflecks indicate that the sunflecks are a limiting factor in the small-scale distribution of K. uniflora.     

Cardiac mitochondrial ATP-sensitive potassium channel is activated by nitric oxide in vitro

Previous observations on the activation of the mitochondrial ATP-sensitive potassium channel (mitoK(ATP)) by nitric oxide (NO) in myocardial preconditioning were based on indirect evidence. In this study, we have investigated the direct effect of NO on the rat cardiac mitoK(ATP) after reconstitution of the inner mitochondrial membranes into lipid bilayers. We found that the mitoK(ATP) was activated by exogenous NO donor S-nitroso-N-acetyl penicillamine or PAPA NONOate. This activation was inhibited by mitoK(ATP) blockers 5-hydroxydecanoate or glibenclamide. Our observations confirm that NO can directly activate the cardiac mitoK(ATP), which may underlie its contribution to myocardial preconditioning.     

An arabinogalactan isolated from the stems of Cistanche deserticola induces the proliferation of cultured lymphocytes

A purified polysaccharide ACDP-2 was isolated from water extract of the stems of Cistanche deserticola. Chemical and spectroscopic analyses indicated that ACDP-2 is a highly branched arabinogalactan polymer that composes of linked d-galactopyranose and d-glucopyranose, which contains predominantly a branching point at the 6-carbon. The branched side-chains compose of terminal-, 1,5-, and 1,3,5-linked arabinofuranosyl residues. ACDP-2 showed an effect in stimulating the immune response, which when applied onto the cultured mouse lymphocytes induced the cell proliferation in a dose-dependent manner.     

Design Method of a Broadband Wide-Angle Plasmonic Absorber in the Visible Range

A new design method of a broadband wide-angle metal-dielectric-metal plasmonic absorber is presented based on the cavity mode theory. The broadband absorption is implemented by filling a unit cell with multi-size square metal patches resonant at adjacent wavelengths, with the widths of the patches and thickness of the dielectric layer optimized with the presented method. A broadband plasmonic absorber working in the visible range is designed, the absorption of which is insensitive to the azimuth angle of incident field and keeps over 0.7 at incident angle up to 60° for p polarization and above 0.6 at up to 40° for s polarization.