Repressing a Repressor

PubMed Central

Silverstone, Aron L.; Jung, Hou-Sung; Dill, Alyssa; Kawaide, Hiroshi; Kamiya, Yuji; Sun, Tai-ping

2001-01-01

RGA (for repressor of ga1-3) and SPINDLY (SPY) are likely repressors of gibberellin (GA) signaling in Arabidopsis because the recessive rga and spy mutations partially suppressed the phenotype of the GA-deficient mutant ga1-3. We found that neither rga nor spy altered the GA levels in the wild-type or the ga1-3 background. However, expression of the GA biosynthetic gene GA4 was reduced 26% by the rga mutation, suggesting that partial derepression of the GA response pathway by rga resulted in the feedback inhibition of GA4 expression. The green fluorescent protein (GFP)–RGA fusion protein was localized to nuclei in transgenic Arabidopsis. This result supports the predicted function of RGA as a transcriptional regulator based on sequence analysis. Confocal microscopy and immunoblot analyses demonstrated that the levels of both the GFP-RGA fusion protein and endogenous RGA were reduced rapidly by GA treatment. Therefore, the GA signal appears to derepress the GA signaling pathway by degrading the repressor protein RGA. The effect of rga on GA4 gene expression and the effect of GA on RGA protein level allow us to identify part of the mechanism by which GA homeostasis is achieved. PMID:11449051

Roles of gibberellins and abscisic acid in dormancy and germination of red bayberry (Myrica rubra) seeds.

PubMed

Chen, Shun-Ying; Kuo, Shing-Rong; Chien, Ching-Te

2008-09-01

Intact seeds from freshly harvested fruits of Myrica rubra (Sieb et Zucc.) were dormant and required 8 weeks of warm stratification followed by 12 weeks of cold stratification for germination. Exogenous application of gibberellic acid (GA(3)) to intact fresh seeds was effective in breaking dormancy, with > 70% of seeds germinating when treated with 5.2 mM GA(3) and incubated at a day/night temperature of 30/20 degrees C for 20 weeks. Removing the hard endocarp or endocarp plus seed coat of fresh seeds promoted germination, and addition of GA(3) to the embryo accelerated germination. The gibberellins GA(1) and GA(4) were more effective than GA(3) in promoting germination of seeds with the endocarp removed. Endogenous contents of GA(1), GA(3), GA(4), GA(7) and GA(20) were quantified by gas chromatography-mass spectrometry-selected ion monitoring in the endocarps, seed coats and embryos of fresh seeds treated with 5.2 mM GA(3). The content of GA(3) decreased in the endocarp during incubation, whereas GA(1) contents increased in the endocarp and seed coat. A high GA(1) content was detected in the endocarps and embryos of newly germinated seeds. We speculate that GA(3) was converted to GA(1) during incubation and that GA(1) is involved in seed germination. Endogenous abscisic acid (ABA) contents were measured in fresh seeds and in warm and cold stratified seeds. The ABA content in fresh seeds was distributed in the order endocarp > seed coat > embryo, with the content in the endocarp being about 132-fold higher than in the seed coat and embryo. Total ABA content of seeds subjected to warm or cold stratification, or both, was 8.7- to 14.0-fold lower than that of fresh seeds. Low contents of endogenous GA(1), GA(3), GA(7) and GA(20), but elevated contents of GA(4), were found in the seed coats and endocarps of warm plus cold stratified seeds and in the seed coats and embryos of newly germinated seeds. These observations, coupled with the finding that GA stimulated germination of dormant Myrica seeds, provide evidence that endogenous ABA inhibited release of dormancy and that endogenous gibberellins, especially GA(4) or GA(1), or both, are involved in germination.

Indole-3-acetic acid modulates phytohormones and polyamines metabolism associated with the tolerance to water stress in white clover.

PubMed

Li, Zhou; Li, Yaping; Zhang, Yan; Cheng, Bizhen; Peng, Yan; Zhang, Xinquan; Ma, Xiao; Huang, Linkai; Yan, Yanhong

2018-06-09

Endogenous hormones and polyamines (PAs) could interact to regulate growth and tolerance to water stress in white clover. The objective of this study was to investigate whether the alteration of endogenous indole-3-acetic acid (IAA) level affected other hormones level and PAs metabolism contributing to the regulation of tolerance to water stress in white clover. Plants were pretreated with IAA or L-2-aminooxy-3-phenylpropionic acid (L-AOPP, the inhibitor of IAA biosynthesis) for 3 days and then subjected to water-sufficient condition and water stress induced by 15% polyethylene glycol 6000 for 8 days in growth chambers. Exogenous application of IAA significantly increased endogenous IAA, gibberellin (GA), abscisic acid (ABA), and polyamine (PAs) levels, but had no effect on cytokinin content under water stress. The increase in endogenous IAA level enhanced PAs anabolism via the improvement of enzyme activities and transcript level of genes including arginine decarboxylase, ornithine decarboxylase, and S-adenosylmethionine decarboxylase. Exogenous application of IAA also affected PAs catabolism, as manifested by an increase in diamine oxidase and a decrease in polyamine oxidase activities and genes expression. More importantly, the IAA deficiency in white clover decreased endogenous hormone levels (GA, ABA, and PAs) and PAs anabolism along with decline in antioxidant defense and osmotic adjustment (OA). On the contrary, exogenous IAA effectively alleviated stress-induced oxidative damage, growth inhibition, water deficit, and leaf senescence through the maintenance of higher chlorophyll content, OA, and antioxidant defense as well as lower transcript levels of senescence marker genes SAG101 and SAG102 in leaves under water stress. These results indicate that IAA-induced the crosstalk between endogenous hormones and PAs could be involved in the improvement of antioxidant defense and OA conferring tolerance to water stress in white clover. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Investigation of plant hormone level changes in shoot tips of longan (Dimocarpus longan Lour.) treated with potassium chlorate by liquid chromatography-electrospray ionization mass spectrometry.

PubMed

Susawaengsup, Chanthana; Rayanakorn, Mongkon; Wongpornchai, Sugunya; Wangkarn, Sunanta

2011-08-15

The endogenous levels of indole-3-acetic acid (IAA), gibberellins (GAs), abscisic acid (ABA) and cytokinins (CKs) and their changes were investigated in shoot tips of ten longan (Dimocarpus longan Lour.) trees for off-season flowering until 60 days after potassium chlorate treatment in comparison with those of ten control (untreated) longan trees. These analytes were extracted and interfering matrices removed with a single mixed-mode solid phase extraction under optimum conditions. The recoveries at three levels of concentration were in the range of 72-112%. The endogenous plant hormones were separated and quantified by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). Detection limits based on the signal-to-noise ratio ranged from 10 ng mL(-1) for gibberellin A4 (GA4) to 200 ng mL(-1) for IAA. Within the first week after potassium chlorate treatment, dry weight (DW) amounts in the treated longan shoot tips of four gibberellins, namely: gibberellin A1(GA1), gibberellic acid (GA3), gibberellin A19 (GA19) and gibberellin A20 (GA20), were found to increase to approximately 25, 50, 20 and 60 ng g(-1) respectively, all of which were significantly higher than those of the controls. In contrast, gibberellin A8 (GA8) obtained from the treated longan was found to decrease to approximately 20 ng g(-1)DW while that of the control increased to around 80 ng g(-1)DW. Certain CKs which play a role in leaf bud induction, particularly isopentenyl adenine (iP), isopentenyl adenosine (iPR) and dihydrozeatin riboside (DHZR), were found to be present in amounts of approximately 20, 50 and 60 ng g(-1)DW in the shoot tips of the control longan. The analytical results obtained from the two-month off-season longan flowering period indicate that high GA1, GA3, GA19 and GA20 levels in the longan shoot tips contribute to flower bud induction while high levels of CKs, IAA and ABA in the control longan contribute more to the vegetative development. Copyright © 2011 Elsevier B.V. All rights reserved.

Gibberellins and gravitropism in maize shoots: endogenous gibberellin-like substances and movement and metabolism of [3H]Gibberellin A20

NASA Technical Reports Server (NTRS)

Rood, S. B.; Kaufman, P. B.; Abe, H.; Pharis, R. P.

1987-01-01

[3H]Gibberellin A20 (GA20) of high specific radioactivity (49.9 gigabecquerel per millimole) was applied equilaterally in a ring of microdrops to the internodal pulvinus of shoots of 3-week-old gravistimulated and vertical normal maize (Zea mays L.), and to a pleiogravitropic (prostrate) maize mutant, lazy (la). All plants converted the [3H]GA20 to [3H]GA1- and [3H]GA29-like metabolites as well as to several metabolites with the partitioning and chromatographic behavior of glucosyl conjugates of [3H]GA1, [3H]GA29, and [3H]GA8. The tentative identification of these putative [3H]GA glucosyl conjugates was further supported by the release of the free [3H]GA moiety after cleavage with cellulase. Within 12 hours of the [3H]GA20 feed, there was a significantly higher proportion of total radioactivity in lower than in upper halves of internode and leaf sheath pulvini in gravistimulated normal maize. Further, there was a significantly higher proportion of putative free GA metabolites of [3H]GA20, especially [3H]GA1, in the lower halves of normal maize relative to upper halves. The differential localization of the metabolites between upper and lower halves was not apparent in the pleiogravitropic mutant, la. Endogenous GA-like substances were also examined in gravistimulated maize shoots. Forty-eight hours after gravistimulation of 3-week-old maize seedlings, endogenous free GA-like substances in upper and lower leaf sheath and internode pulvini halves were extracted, chromatographed, and bioassayed using the "Tanginbozu" dwarf rice microdrop assay. Lower halves contained consistently higher total levels of GA-like activity. The qualitative elution profile of GA-like substances differed consistently, upper halves containing principally a GA20-like substance and lower halves containing principally a GA20-like substance and lower halves containing mainly GA1-like and GA19-like substances. Gibberellins A1 (10 nanograms per gram) and A20 (5 nanograms per gram) were identified from these lower leaf sheath pulvini by capillary gas chromatography-selected ion monitoring. Results from all of these experiments are consistent with a role for GAs in the differential shoot growth that follows gravitropism, although the results do not eliminate the possibility that the redistribution of GAs results from the gravitropic response.

Water Deficit Affected Flavonoid Accumulation by Regulating Hormone Metabolism in Scutellaria baicalensis Georgi Roots

PubMed Central

Wu, Chong; Chen, Shunqin; Wang, Zhouyong; Yang, Zhaochun; Qin, Shuangshuang; Huang, Luqi

2012-01-01

The content of flavonoids especially baicalin and baicalein determined the medical quality of Scutellaria baicalensis which is a Chinese traditional medicinal plant. Here, we investigated the mechanism responsible for the content and composition of flavonoids in S. baicalensis under water deficit condition. The transcription levels of several genes which are involved in flavonoid biosynthesis were stimulated by water deficit. Under water deficit condition, fifteen up-regulated proteins, three down-regulated proteins and other six proteins were detected by proteomic analysis. The identified proteins include three gibberellin (GA)- or indoleacetic acid (IAA)-related proteins. Decreased endogenous GAs level and increased IAA level were observed in leaves of S. baicalensis which was treated with water deficit. Exogenous application of GA or α-naphthalene acelic acid (NAA) to plants grown under water deficit conditions led to the increase of endogenous GAs and the decrease of IAA and flavonoids, respectively. When the synthesis pathway of GA or IAA in plants was inhibited by application with the inhibitors, flavonoid levels were recovered. These results indicate that water deficit affected flavonoid accumulation might through regulating hormone metabolism in S. baicalensis Georgi. PMID:23077481

Abscisic acid in the thermoinhibition of lettuce seed germination and enhancement of its catabolism by gibberellin.

PubMed

Gonai, Takeru; Kawahara, Shusuke; Tougou, Makoto; Satoh, Shigeru; Hashiba, Teruyoshi; Hirai, Nobuhiro; Kawaide, Hiroshi; Kamiya, Yuji; Yoshioka, Toshihito

2004-01-01

Germination of lettuce (Lactuca sativa L. cv. 'Grand Rapids') seeds was inhibited at high temperatures (thermoinhibition). Thermoinhibition at 28 degrees C was prevented by the application of fluridone, an inhibitor of abscisic acid (ABA) biosynthesis. At 33 degrees C, the sensitivity of the seeds to ABA increased, and fluridone on its own was no longer effective. However, a combined application of fluridone and gibberellic acid (GA3) was able to restore the germination. Exogenous GA3 lowered endogenous ABA content in the seeds, enhancing catabolism of ABA and export of the catabolites from the intact seeds. The fluridone application also decreased the ABA content. Consequently, the combined application of fluridone and GA3 decreased the ABA content to a sufficiently low level to allow germination at 33 degrees C. There was no significant temperature-dependent change in endogenous GA1 contents. It is concluded that ABA is an important factor in the regulation of thermoinhibition of lettuce seed germination, and that GA affects the temperature responsiveness of the seeds through ABA metabolism.

Ectopic Expression of Pumpkin Gibberellin Oxidases Alters Gibberellin Biosynthesis and Development of Transgenic Arabidopsis Plants1

PubMed Central

Radi, Abeer; Lange, Theo; Niki, Tomoya; Koshioka, Masaji; Lange, Maria João Pimenta

2006-01-01

Immature pumpkin (Cucurbita maxima) seeds contain gibberellin (GA) oxidases with unique catalytic properties resulting in GAs of unknown function for plant growth and development. Overexpression of pumpkin GA 7-oxidase (CmGA7ox) in Arabidopsis (Arabidopsis thaliana) resulted in seedlings with elongated roots, taller plants that flower earlier with only a little increase in bioactive GA4 levels compared to control plants. In the same way, overexpression of the pumpkin GA 3-oxidase1 (CmGA3ox1) resulted in a GA overdose phenotype with increased levels of endogenous GA4. This indicates that, in Arabidopsis, 7-oxidation and 3-oxidation are rate-limiting steps in GA plant hormone biosynthesis that control plant development. With an opposite effect, overexpression of pumpkin seed-specific GA 20-oxidase1 (CmGA20ox1) in Arabidopsis resulted in dwarfed plants that flower late with reduced levels of GA4 and increased levels of physiological inactive GA17 and GA25 and unexpected GA34 levels. Severe dwarfed plants were obtained by overexpression of the pumpkin GA 2-oxidase1 (CmGA2ox1) in Arabidopsis. This dramatic change in phenotype was accompanied by a considerable decrease in the levels of bioactive GA4 and an increase in the corresponding inactivation product GA34 in comparison to control plants. In this study, we demonstrate the potential of four pumpkin GA oxidase-encoding genes to modulate the GA plant hormone pool and alter plant stature and development. PMID:16384902

Stamen-derived bioactive gibberellin is essential for male flower development of Cucurbita maxima L.

PubMed Central

Pimenta Lange, Maria João; Knop, Nicole; Lange, Theo

2012-01-01

Gibberellin (GA) signalling during pumpkin male flower development is highly regulated, including biosynthetic, perception, and transduction pathways. GA 20-oxidases, 3-oxidases, and 2-oxidases catalyse the final part of GA synthesis. Additionally, 7-oxidase initiates this part of the pathway in some cucurbits including Cucurbita maxima L. (pumpkin). Expression patterns for these GA-oxidase-encoding genes were examined by competitive reverse transcription-PCR (RT-PCR) and endogenous GA levels were determined during pumpkin male flower development. In young flowers, GA20ox3 transcript levels are high in stamens, followed by high levels of the GA precursor GA9. Later, just before flower opening, transcript levels for GA3ox3 and GA3ox4 increase in the hypanthium and stamens, respectively. In the stamen, following GA3ox4 expression, bioactive GA4 levels rise dramatically. Accordingly, catabolic GA2ox2 and GA2ox3 transcript levels are low in developing flowers, and increase in mature flowers. Putative GA receptor GID1b and DELLA repressor GAIPb transcript levels do not change in developing flowers, but increase sharply in mature flowers. Emasculation arrests floral development completely and leads to abscission of premature flowers. Application of GA4 (but not of its precursors GA12-aldehyde or GA9) restores normal growth of emasculated flowers. These results indicate that de novo GA4 synthesis in the stamen is under control of GA20ox3 and GA3ox4 genes just before the rapid flower growth phase. Stamen-derived bioactive GA is essential and sufficient for male flower development, including the petal and the pedicel growth. PMID:22268154

Gibberellins and stem growth in Arabidopsis thaliana. Effects of photoperiod on expression of the GA4 and GA5 loci.

PubMed

Xu, Y L; Gage, D A; Zeevaart, J A

1997-08-01

Arabidopsis thaliana (L.) Heynh. is a quantitative long-day (LD) rosette plant in which stem growth is mediated by gibberellins (CAs). Application of GAs to plants in short-day (SD) conditions resulted in rapid stem elongation and flower formation, with GA4 and GA9 being equally effective, and GA1 showing lower activity. The effects of photoperiod on the levels of endogenous GAs were measured by combined gas chromatography-mass spectrometry with selected ion monitoring. When plants were transferred from SD to LD conditions there was a slight decrease in the level of GA53 and an increase in the levels of C19-GAs, GA9, GA20, GA1, and GA8, indicating that GA 20-oxidase activity is stimulated in LD conditions. Expression of GA5, which encodes GA 20-oxidase, was highest in elongating stems and was correlated with the rate of stem elongation. By contrast, GA4, which encodes 3 beta-hydroxylase, showed low expression in stems and its expression was not correlated with the rate of stem elongation. We conclude that stem elongation in LD conditions is at least in part due to increased expression of GA5, whereas expression of GA4 is not under photoperiodic control.

Temperature Regulation of Endogenous Gibberellin Activity and Development of Tulipa gesneriana L. 1

PubMed Central

Aung, L. H.; De Hertogh, A. A.; Staby, G.

1969-01-01

The changes in the contents of free and bound gibberellin-like activity (GA) of Tulipa gesneriana L. cv. Ralph during development under 2 temperature conditions were studied. The results show that the content of free GA of bulbs grown at 18° increased by 67% over the initial level during development. The bound GA showed a slight initial increase and was followed by a rapid decrease. In contrast, bulbs treated at 13° showed a marked decline in free GA and a 2-fold increase in the content of bound GA. However, after the transfer of these bulbs from 13° to 18° the free GA increased to the initial level while the bound GA decreased to a low level. The rate of floral shoot and root development and time of flowering were accelerated at 18° as compared to 13°. From the data obtained, it was suggested that a temperature-sensitive interconversion mechanism between free and bound GA exists in tulip bulbs and that there is apparent synthesis or transformation of these phytohormones during development of the bulbs. PMID:16657075

Gibberellin Biosynthesis in Developing Pumpkin Seedlings12

PubMed Central

Lange, Theo; Kappler, Jeannette; Fischer, Andreas; Frisse, Andrea; Padeffke, Tania; Schmidtke, Sabine; Lange, Maria João Pimenta

2005-01-01

A gibberellin (GA) biosynthetic pathway was discovered operating in root tips of 7-d-old pumpkin (Cucurbita maxima) seedlings. Stepwise analysis of GA metabolism in cell-free systems revealed the conversion of GA12-aldehyde to bioactive GA4 and inactive GA34. Highest levels of endogenous GA4 and GA34 were found in hypocotyls and root tips of 3-d-old seedlings. cDNA molecules encoding two GA oxidases, CmGA20ox3 and CmGA3ox3, were isolated from root tips of 7-d-old LAB150978-treated seedlings. Recombinant CmGA20ox3 fusion protein converted GA12 to GA9, GA24 to GA9, GA14 to GA4, and, less efficiently, GA53 to GA20, and recombinant CmGA3ox3 protein oxidized GA9 to GA4. Transcript profiles were determined for four GA oxidase genes from pumpkin revealing relatively high transcript levels for CmGA7ox in shoot tips and cotyledons, for CmGA20ox3 in shoot tips and hypocotyls, and for CmGA3ox3 in hypocotyls and roots of 3-d-old seedlings. Transcripts of CmGA2ox1 were mainly found in roots of 7-d-old seedlings. In roots of 7-d-old seedlings, transcripts of CmGA7ox, CmGA20ox3, and CmGA3ox3 were localized in the cap and the rhizodermis by in situ hybridization. We conclude that hypocotyls and root tips are important sites of GA biosynthesis in the developing pumpkin seedling. PMID:16126862

Gibberellins regulate iron deficiency-response by influencing iron transport and translocation in rice seedlings (Oryza sativa)

PubMed Central

Wang, Baolan; Wei, Haifang; Xue, Zhen

2017-01-01

Background and aims Gibberellins (GAs) are a class of plant hormones with diverse functions. However, there has been little information on the role of GAs in response to plant nutrient deficiency. Methods To evaluate the roles of GAs in regulation of Fe homeostasis, the effects of GA on Fe accumulation and Fe translocation in rice seedlings were investigated using wild-type, a rice mutant (eui1) displaying enhnaced endogenous GA concentrations due to a defect in GA deactivation, and transgenic rice plants overexpressing OsEUI. Key Results Exposure to Fe-deficient medium significantly reduced biomass of rice plants. Both exogenous application of GA and an endogenous increase of bioactive GA enhanced Fe-deficiency response by exaggerating foliar chlorosis and reducing growth. Iron deficiency significantly suppressed production of GA1 and GA4, the biologically active GAs in rice. Exogenous application of GA significantly decreased leaf Fe concentration regardless of Fe supply. Iron concentration in shoot of eui1 mutants was lower than that of WT plants under both Fe-sufficient and Fe-deficient conditions. Paclobutrazol, an inhibitor of GA biosynthesis, alleviated Fe-deficiency responses, and overexpression of EUI significantly increased Fe concentration in shoots and roots. Furthermore, both exogenous application of GA and endogenous increase in GA resulting from EUI mutation inhibited Fe translocation within shoots by suppressing OsYSL2 expression, which is involved in Fe transport and translocation. Conclusions The novel findings provide compelling evidence to support the involvement of GA in mediation of Fe homeostasis in strategy II rice plants by negatively regulating Fe transport and translocation. PMID:28065924

Seed-borne endophytic Bacillus amyloliquefaciens RWL-1 produces gibberellins and regulates endogenous phytohormones of Oryza sativa.

PubMed

Shahzad, Raheem; Waqas, Muhammad; Khan, Abdul Latif; Asaf, Sajjad; Khan, Muhammad Aaqil; Kang, Sang-Mo; Yun, Byung-Wook; Lee, In-Jung

2016-09-01

Some microorganisms are adapted to an endophytic mode, living symbiotically with plants through vertical transmission in seeds. The role of plant growth-promoting endophytes has been well studied, but those of seed-associated endophytic bacteria are less understood. The current study aimed to isolate and identify bacterial endophytes associated with rice (Oryza sativa L. 'Jin so mi') seeds, their potential to produce gibberellins (GAs), and role in improving host-plant physiology. The isolated bacterial endophyte RWL-1 was identified as Bacillus amyloliquefaciens by using 16S rRNA sequencing and phylogenetic analysis. The pure culture of B. amyloliquefaciens RWL-1, supplied with deuterated internal standards, was subjected to gas chromatography and mass spectrometric selected ion monitoring (GC-MS/SIM) for quantification of GAs. Results showed the presence of GAs in various quantities (ng/mL) viz., GA20 (17.88 ± 4.04), GA36 (5.75 ± 2.36), GA24 (5.64 ± 2.46), GA4 (1.02 ± 0.16), GA53 (0.772 ± 0.20), GA9 (0.12 ± 0.09), GA19 (0.093 ± 0.13), GA5 (0.08 ± 0.04), GA12 (0.014 ± 0.34), and GA8 (0.013 ± 0.01). Since endogenous seed GAs are essential for prolonged seed growth and subsequent plant development, we used exogenous GA3 as a positive control and water as a negative control for comparative analysis of the application of B. amyloliquefaciens RWL-1 to rice plants. The growth parameters of rice plants treated with endophytic bacterial cell application was significantly increased compared to the plants treated with exogenous GA3 and water. This was also revealed by the significant up-regulation of endogenous GA1 (17.54 ± 2.40 ng), GA4 (310 ± 5.41 ng), GA7 (192.60 ± 3.32 ng), and GA9 (19.04 ± 2.49 ng) as compared to results of the positive and negative control treatments. Rice plants inoculated with B. amyloliquefaciens RWL-1 exhibited significantly higher endogenous salicylic acid (1615.06 ± 10.81 μg), whereas endogenous abscisic acid (23.31 ± 2.76 ng) and jasmonic acid (25.51 ± 4.20 ng) were observed to be significantly lower in these inoculated plants than in those treated with exogenous GA3 and water. Results of the present study suggest that B. amyloliquefaciens RWL-1 has the ability to produce GAs and that its inoculation in seedlings can be beneficial to rice plants. Broader field trials should be conducted to determine its use as an alternative biofertilizer. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Molecular Mechanisms Underlying Abscisic Acid/Gibberellin Balance in the Control of Seed Dormancy and Germination in Cereals

PubMed Central

Tuan, Pham A.; Kumar, Rohit; Rehal, Pawanpuneet K.; Toora, Parneet K.; Ayele, Belay T.

2018-01-01

Seed dormancy is an adaptive trait that does not allow the germination of an intact viable seed under favorable environmental conditions. Non-dormant seeds or seeds with low level of dormancy can germinate readily under optimal environmental conditions, and such a trait leads to preharvest sprouting, germination of seeds on the mother plant prior to harvest, which significantly reduces the yield and quality of cereal crops. High level of dormancy, on the other hand, may lead to non-uniform germination and seedling establishment. Therefore, intermediate dormancy is considered to be a desirable trait as it prevents the problems of sprouting and allows uniformity of postharvest germination of seeds. Induction, maintenance, and release of seed dormancy are complex physiological processes that are influenced by a wide range of endogenous and environmental factors. Plant hormones, mainly abscisic acid (ABA) and gibberellin (GA), are the major endogenous factors that act antagonistically in the control of seed dormancy and germination; ABA positively regulates the induction and maintenance of dormancy, while GA enhances germination. Significant progress has been made in recent years in the elucidation of molecular mechanisms regulating ABA/GA balance and thereby dormancy and germination in cereal seeds, and this review summarizes the current state of knowledge on the topic. PMID:29875780

Ribonucleic Acid Synthesis by Cucumber Chromatin

PubMed Central

Johnson, Kenneth D.; Purves, William K.

1970-01-01

When intact etiolated 2-day cucumber (Cucumis sativus) embryos were treated with indoleacetic acid (IAA), gibberellin A7 (GA7), or kinetin, chromatin derived from the embryonic axes exhibited an increased capacity to support RNA synthesis in either the presence or the absence of bacterial RNA polymerase. An IAA effect on cucumber RNA polymerase activity was evident after 4 hours of hormone treatment; the IAA effect on DNA template activity (bacterial RNA polymerase added) occurred after longer treatments (12 hours). GA7 also promoted template activity, but again only after a prior stimulation of endogenous chromatin activity. After 12 hours of kinetin treatment, both endogenous chromatin and DNA template activities were substantially above control values, but longer kinetin treatments caused these activities to decline in magnitude. When chromatin was prepared from hypocotyl segments that were floated on a GA7 solution, a GA-induced increase in endogenous chromatin activity occurred, but only if cotyledon tissue was left attached to the segments during the period of hormone treatment. Age of the seedling tissue had a profound influence on the chromatin characteristics. With progression of development from the 2-day to the 4-day stage, the endogenous chromatin activity declined while the DNA template activity increased. PMID:16657509

Gibberellins regulate iron deficiency-response by influencing iron transport and translocation in rice seedlings (Oryza sativa).

PubMed

Wang, Baolan; Wei, Haifang; Xue, Zhen; Zhang, Wen-Hao

2017-04-01

Gibberellins (GAs) are a class of plant hormones with diverse functions. However, there has been little information on the role of GAs in response to plant nutrient deficiency. To evaluate the roles of GAs in regulation of Fe homeostasis, the effects of GA on Fe accumulation and Fe translocation in rice seedlings were investigated using wild-type, a rice mutant ( eui1 ) displaying enhnaced endogenous GA concentrations due to a defect in GA deactivation, and transgenic rice plants overexpressing OsEUI . Exposure to Fe-deficient medium significantly reduced biomass of rice plants. Both exogenous application of GA and an endogenous increase of bioactive GA enhanced Fe-deficiency response by exaggerating foliar chlorosis and reducing growth. Iron deficiency significantly suppressed production of GA 1 and GA 4 , the biologically active GAs in rice. Exogenous application of GA significantly decreased leaf Fe concentration regardless of Fe supply. Iron concentration in shoot of eui1 mutants was lower than that of WT plants under both Fe-sufficient and Fe-deficient conditions. Paclobutrazol, an inhibitor of GA biosynthesis, alleviated Fe-deficiency responses, and overexpression of EUI significantly increased Fe concentration in shoots and roots. Furthermore, both exogenous application of GA and endogenous increase in GA resulting from EUI mutation inhibited Fe translocation within shoots by suppressing OsYSL2 expression, which is involved in Fe transport and translocation. The novel findings provide compelling evidence to support the involvement of GA in mediation of Fe homeostasis in strategy II rice plants by negatively regulating Fe transport and translocation. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Ectopic expression of GA 2-oxidase 6 from rapeseed (Brassica napus L.) causes dwarfism, late flowering and enhanced chlorophyll accumulation in Arabidopsis thaliana.

PubMed

Yan, Jindong; Liao, Xiaoying; He, Reqing; Zhong, Ming; Feng, Panpan; Li, Xinmei; Tang, Dongying; Liu, Xuanming; Zhao, Xiaoying

2017-02-01

Gibberellins (GAs) are endogenous hormones that play an important role in higher plant growth and development. GA2-oxidase (GA2ox) promotes catabolism and inactivation of bioactive GAs or their precursors. In this study, we identified the GA2-oxidase gene, BnGA2ox6, and found it to be highly expressed in the silique and flower. Overexpression of BnGA2ox6 in Arabidopsis resulted in GA-deficiency symptoms, including inhibited elongation of the hypocotyl and stem, delayed seed germination, and late flowering. BnGA2ox6 overexpression reduced silique growth, but had no effect on seed development. Additionally, BnGA2ox6 overexpression enhanced chlorophyll b and total chlorophyll accumulation, and downregulated mRNA expression levels of the CHL1 and RCCR genes, which are involved in the chlorophyll degradation. These findings suggest that BnGA2ox6 regulates plant hight, silique development, flowering and chlorophyll accumulation in transgenic Arabidopsis. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Gibberellins and Gravitropism in Maize Shoots 1

PubMed Central

Rood, Stewart B.; Kaufman, Peter B.; Abe, Hiroshi; Pharis, Richard P.

1987-01-01

[3H]Gibberellin A20 (GA20) of high specific radioactivity (49.9 gigabecquerel per millimole) was applied equilaterally in a ring of microdrops to the internodal pulvinus of shoots of 3-week-old gravistimulated and vertical normal maize (Zea mays L.), and to a pleiogravitropic (prostrate) maize mutant, lazy (la). All plants converted the [3H]GA20 to [3H]GA1− and [3H]GA29-like metabolites as well as to several metabolites with the partitioning and chromatographic behavior of glucosyl conjugates of [3H]GA1, [3H]GA29, and [3H]GA8. The tentative identification of these putative [3H]GA glucosyl conjugates was further supported by the release of the free [3H]GA moiety after cleavage with cellulase. Within 12 hours of the [3H]GA20 feed, there was a significantly higher proportion of total radioactivity in lower than in upper halves of internode and leaf sheath pulvini in gravistimulated normal maize. Further, there was a significantly higher proportion of putative free GA metabolites of [3H]GA20, especially [3H]GA1, in the lower halves of normal maize relative to upper halves. The differential localization of the metabolites between upper and lower halves was not apparent in the pleiogravitropic mutant, la. Endogenous GA-like substances were also examined in gravistimulated maize shoots. Forty-eight hours after gravistimulation of 3-week-old maize seedlings, endogenous free GA-like substances in upper and lower leaf sheath and internode pulvini halves were extracted, chromatographed, and bioassayed using the `Tanginbozu' dwarf rice microdrop assay. Lower halves contained consistently higher total levels of GA-like activity. The qualitative elution profile of GA-like substances differed consistently, upper halves containing principally a GA20-like substance and lower halves containing mainly GA1-like and GA19-like substances. Gibberellins A1 (10 nanograms per gram) and A20 (5 nanograms per gram) were identified from these lower leaf sheath pulvini by capillary gas chromatography-selected ion monitoring. Results from all of these experiments are consistent with a role for GAs in the differential shoot growth that follows gravitropism, although the results do not eliminate the possibility that the redistribution of GAs results from the gravitropic response. Images Fig. 1 PMID:11539033

Overexpression of Jatropha Gibberellin 2-oxidase 6 (JcGA2ox6) Induces Dwarfism and Smaller Leaves, Flowers and Fruits in Arabidopsis and Jatropha

PubMed Central

Hu, Ying-Xiong; Tao, Yan-Bin; Xu, Zeng-Fu

2017-01-01

Gibberellins (GAs) are plant hormones that play fundamental roles in plant growth and development. Gibberellin 2-oxidase (GA2ox) plays a direct role in determining the levels of bioactive GAs by catalyzing bioactive GAs or their immediate precursors to inactive forms. In this study, a GA2ox gene, designated JcGA2ox6, was isolated from Jatropha curcas. JcGA2ox6 is expressed in all tissues of adult Jatropha, with the highest expression level in male flowers and the lowest expression level in young leaves. Overexpression of JcGA2ox6 in Arabidopsis resulted in a typical dwarf phenotype, along with late flowering, smaller leaves and flowers, shorter siliques and smaller seeds. Similarly, when JcGA2ox6 was overexpressed in Jatropha, the transgenic plants exhibited a dwarf phenotype with dark-green leaves and smaller inflorescences, flowers, fruits and seeds. However, the flowering time of Jatropha was not affected by overexpression of JcGA2ox6, unlike that in the transgenic Arabidopsis. Moreover, the number of flowers per inflorescence, the weight of 10 seeds and the seed oil content were significantly decreased in transgenic Jatropha. The results indicated that overexpression of JcGA2ox6 had a great impact on the vegetative and reproductive growth of transgenic Jatropha. Furthermore, we found that the dwarf phenotype of transgenic Jatropha was caused by a decrease in endogenous bioactive GA4, which was correlated with the degree of dwarfism. PMID:29312375

Reduction of gibberellin by low temperature disrupts pollen development in rice.

PubMed

Sakata, Tadashi; Oda, Susumu; Tsunaga, Yuta; Shomura, Hikaru; Kawagishi-Kobayashi, Makiko; Aya, Koichiro; Saeki, Kenichi; Endo, Takashi; Nagano, Kuniaki; Kojima, Mikiko; Sakakibara, Hitoshi; Watanabe, Masao; Matsuoka, Makoto; Higashitani, Atsushi

2014-04-01

Microsporogenesis in rice (Oryza sativa) plants is susceptible to moderate low temperature (LT; approximately 19°C) that disrupts pollen development and causes severe reductions in grain yields. Although considerable research has been invested in the study of cool-temperature injury, a full understanding of the molecular mechanism has not been achieved. Here, we show that endogenous levels of the bioactive gibberellins (GAs) GA4 and GA7, and expression levels of the GA biosynthesis genes GA20ox3 and GA3ox1, decrease in the developing anthers by exposure to LT. By contrast, the levels of precursor GA12 were higher in response to LT. In addition, the expression of the dehydration-responsive element-binding protein DREB2B and SLENDER RICE1 (SLR1)/DELLA was up-regulated in response to LT. Mutants involved in GA biosynthetic and response pathways were hypersensitive to LT stress, including the semidwarf mutants sd1 and d35, the gain-of-function mutant slr1-d, and gibberellin insensitive dwarf1. The reduction in the number of sporogenous cells and the abnormal enlargement of tapetal cells occurred most severely in the GA-insensitive mutant. Application of exogenous GA significantly reversed the male sterility caused by LT, and simultaneous application of exogenous GA with sucrose substantially improved the extent of normal pollen development. Modern rice varieties carrying the sd1 mutation are widely cultivated, and the sd1 mutation is considered one of the greatest achievements of the Green Revolution. The protective strategy achieved by our work may help sustain steady yields of rice under global climate change.

Endogenous Gibberellins of Pine Pollen

PubMed Central

Kamienska, Aniela; Pharis, Richard P.

1975-01-01

The endogenous gibberellins (GAs) of pollen of Pinus attenuata, P. coulteri, and P. ponderosa were bioassayed at hour 0, 3, 15, 24, 48 and 72 of germination. Dormant pollen showed relatively high GA activity throughout the elution spectrum (i.e. ranging from relatively nonpolar to highly polar). The maximum GA activity was obtained at hour 15 in more polar regions and especially in the zone corresponding to GA3 (for P. attenuata estimated as 250 micrograms of GA3/kilogram pollen). It is probable that the “nonpolar” GAs present in high quantities in dormant pollen and in early stages of germination were converted to “more polar” GAs as germination progressed. The amount of all GAs decreased after hour 15 of germination and by hour 72 no GAs could be detected. Among the species tested P. attenuata showed the highest over-all GA activity. PMID:16659365

Activation of gibberellin 2-oxidase 6 decreases active gibberellin levels and creates a dominant semi-dwarf phenotype in rice (Oryza sativa L.).

PubMed

Huang, Jian; Tang, Ding; Shen, Yi; Qin, Baoxiang; Hong, Lilan; You, Aiqing; Li, Ming; Wang, Xin; Yu, Hengxiu; Gu, Minghong; Cheng, Zhukuan

2010-01-01

Gibberellin (GA) 2-oxidase plays a key role in the GA catabolic pathway through 2beta-hydroxylation. In the present study, we isolated a CaMV 35S-enhancer activation tagged mutant, H032. This mutant exhibited a dominant dwarf and GA-deficient phenotype, with a final stature that was less than half of its wild-type counterpart. The endogenous bioactive GAs are markedly decreased in the H032 mutant, and application of bioactive GAs (GA(3) or GA(4)) can reverse the dwarf phenotype. The integrated T-DNA was detected 12.8 kb upstream of the OsGA2ox6 in the H032 genome by TAIL-PCR. An increased level of OsGA2ox6 mRNA was detected at a high level in the H032 mutant, which might be due to the enhancer role of the CaMV 35S promoter. RNAi and ectopic expression analysis of OsGA2ox6 indicated that the dwarf trait and the decreased levels of bioactive GAs in the H032 mutant were a result of the up-regulation of the OsGA2ox6 gene. BLASTP analysis revealed that OsGA2ox6 belongs to the class III of GA 2-oxidases, which is a novel type of GA2ox that uses C20-GAs (GA(12) and/or GA(53)) as the substrates. Interestingly, we found that a GA biosynthesis inhibitor, paclobutrazol, positively regulated the OsGA2ox6 gene. Unlike the over-expression of OsGA2ox1, which led to a high rate of seed abortion, the H032 mutant retained normal flowering and seed production. These results indicate that OsGA2ox6 mainly affects plant stature, and the dominant dwarf trait of the H032 mutant can be used as an efficient dwarf resource in rice breeding. Copyright 2010 Institute of Genetics and Developmental Biology and the Genetics Society of China. Published by Elsevier Ltd. All rights reserved.

Gonadotropin Promotion of Adventitious Root Production on Cuttings of Begonia semperflorens and Vitis vinifera 1

PubMed Central

Leshem, Y.; Lunenfeld, B.

1968-01-01

Adventitious rooting of Begonia semperflorens cv. Indian Maid and Vitis vinifera cv. Semillon stem cuttings was significantly promoted by human chorionic gonadotropin (HCG). Basal sections of HCG treated cuttings upon which promoted rooting took place had markedly less endogenous gibberellin (GA) activity than non-treated controls or apical sections of treated ones, while changes in auxin levels were not found. HCG also inhibited GA3-induced reducing sugar release from embryoless barley endosperm halves. These findings are discussed in the light of a possible analogy to gonadotropin action in animal systems. PMID:5641189

A novel class of gibberellin 2-oxidases control semidwarfism, tillering, and root development in rice.

PubMed

Lo, Shuen-Fang; Yang, Show-Ya; Chen, Ku-Ting; Hsing, Yue-Ie; Zeevaart, Jan A D; Chen, Liang-Jwu; Yu, Su-May

2008-10-01

Gibberellin 2-oxidases (GA2oxs) regulate plant growth by inactivating endogenous bioactive gibberellins (GAs). Two classes of GA2oxs inactivate GAs through 2beta-hydroxylation: a larger class of C(19) GA2oxs and a smaller class of C(20) GA2oxs. In this study, we show that members of the rice (Oryza sativa) GA2ox family are differentially regulated and act in concert or individually to control GA levels during flowering, tillering, and seed germination. Using mutant and transgenic analysis, C(20) GA2oxs were shown to play pleiotropic roles regulating rice growth and architecture. In particular, rice overexpressing these GA2oxs exhibited early and increased tillering and adventitious root growth. GA negatively regulated expression of two transcription factors, O. sativa homeobox 1 and TEOSINTE BRANCHED1, which control meristem initiation and axillary bud outgrowth, respectively, and that in turn inhibited tillering. One of three conserved motifs unique to the C(20) GA2oxs (motif III) was found to be important for activity of these GA2oxs. Moreover, C(20) GA2oxs were found to cause less severe GA-defective phenotypes than C(19) GA2oxs. Our studies demonstrate that improvements in plant architecture, such as semidwarfism, increased root systems and higher tiller numbers, could be induced by overexpression of wild-type or modified C(20) GA2oxs.

Reduction of Gibberellin by Low Temperature Disrupts Pollen Development in Rice1[W][OPEN

PubMed Central

Sakata, Tadashi; Oda, Susumu; Tsunaga, Yuta; Shomura, Hikaru; Kawagishi-Kobayashi, Makiko; Aya, Koichiro; Saeki, Kenichi; Endo, Takashi; Nagano, Kuniaki; Kojima, Mikiko; Sakakibara, Hitoshi; Watanabe, Masao; Matsuoka, Makoto; Higashitani, Atsushi

2014-01-01

Microsporogenesis in rice (Oryza sativa) plants is susceptible to moderate low temperature (LT; approximately 19°C) that disrupts pollen development and causes severe reductions in grain yields. Although considerable research has been invested in the study of cool-temperature injury, a full understanding of the molecular mechanism has not been achieved. Here, we show that endogenous levels of the bioactive gibberellins (GAs) GA4 and GA7, and expression levels of the GA biosynthesis genes GA20ox3 and GA3ox1, decrease in the developing anthers by exposure to LT. By contrast, the levels of precursor GA12 were higher in response to LT. In addition, the expression of the dehydration-responsive element-binding protein DREB2B and SLENDER RICE1 (SLR1)/DELLA was up-regulated in response to LT. Mutants involved in GA biosynthetic and response pathways were hypersensitive to LT stress, including the semidwarf mutants sd1 and d35, the gain-of-function mutant slr1-d, and gibberellin insensitive dwarf1. The reduction in the number of sporogenous cells and the abnormal enlargement of tapetal cells occurred most severely in the GA-insensitive mutant. Application of exogenous GA significantly reversed the male sterility caused by LT, and simultaneous application of exogenous GA with sucrose substantially improved the extent of normal pollen development. Modern rice varieties carrying the sd1 mutation are widely cultivated, and the sd1 mutation is considered one of the greatest achievements of the Green Revolution. The protective strategy achieved by our work may help sustain steady yields of rice under global climate change. PMID:24569847

The rice YABBY1 gene is involved in the feedback regulation of gibberellin metabolism.

PubMed

Dai, Mingqiu; Zhao, Yu; Ma, Qian; Hu, Yongfeng; Hedden, Peter; Zhang, Qifa; Zhou, Dao-Xiu

2007-05-01

Gibberellin (GA) biosynthesis is regulated by feedback control providing a mechanism for GA homeostasis in plants. However, regulatory elements involved in the feedback control are not known. In this report, we show that a rice (Oryza sativa) YABBY1 (YAB1) gene had a similar expression pattern as key rice GA biosynthetic genes GA3ox2 and GA20ox2. Overexpression of YAB1 in transgenic rice resulted in a semidwarf phenotype that could be fully rescued by applied GA. Quantification of the endogenous GA content revealed increases of GA(20) and decreases of GA(1) levels in the overexpression plants, in which the transcripts of the biosynthetic gene GA3ox2 were decreased. Cosuppression of YAB1 in transgenic plants induced expression of GA3ox2. The repression of GA3ox2 could be obtained upon treatment by dexamethasone of transgenic plants expressing a YAB1-glucocorticoid receptor fusion. Importantly, we show that YAB1 bound to a GA-responsive element within the GA3ox2 promoter. In addition, the expression of YAB1 was deregulated in GA biosynthesis and signaling mutants and could be either transiently induced by GA or repressed by a GA inhibitor. Finally, either overexpression or cosuppression of YAB1 impaired GA-mediated repression of GA3ox2. These data together suggest that YAB1 is involved in the feedback regulation of GA biosynthesis in rice.

Enterobacter sp. I-3, a bio-herbicide inhibits gibberellins biosynthetic pathway and regulates abscisic acid and amino acids synthesis to control plant growth.

PubMed

Radhakrishnan, Ramalingam; Park, Jae-Man; Lee, In-Jung

2016-12-01

Very few bacterial species were identified as bio-herbicides for weed control. The present research was focused to elucidate the plant growth retardant properties of Enterobacter sp. I-3 during their interaction by determining the changes in endogenous photosynthetic pigments, plant hormones and amino acids. The two bacterial isolates I-4-5 and I-3 were used to select the superior bacterium for controlling weed seeds (Echinochloa crus-galli L. and Portulaca oleracea L.) germination. The post-inoculation of I-3 (Enterobacter sp. I-3) significantly inhibited the weeds seed germination than their controls. The mechanism of bacterium induced plant growth reduction was identified in lettuce treated with I-3 bacterium and compared their effects with known chemical herbicide, trinexapac-ethyl (TE). The treatment of I-3 and TE showed a significant inhibitory effect on shoot length, leaf number, leaf length, leaf width, shoot weight, root weight and chlorophyll content in lettuce seedlings. The endogenous gibberellins (GAs) and abscisic acid (ABA) analysis showed that Enterobacter sp. I-3 treated plants had lower levels of GAs (GA 12 , GA 19 , GA 20 and GA 8 ) and GAs/ABA ratio and then, the higher level of ABA when compared to their controls. Indeed, the individual amino acids ie., aspartic acid, glutamic acid, glycine, threonine, alanine, serine, leucine, isoleucine and tyrosine were declined in TE and I-3 exposed plants. Our results suggest that the utilization of Enterobacter sp. I-3 inhibits the GAs pathway and amino acids synthesis in weeds to control their growth can be an alternative to chemical herbicides. Copyright © 2016 Elsevier GmbH. All rights reserved.

Production of Dwarf Lettuce by Overexpressing a Pumpkin Gibberellin 20-Oxidase Gene

PubMed Central

Niki, Tomoya; Nishijima, Takaaki; Nakayama, Masayoshi; Hisamatsu, Tamotsu; Oyama-Okubo, Naomi; Yamazaki, Hiroko; Hedden, Peter; Lange, Theo; Mander, Lewis N.; Koshioka, Masaji

2001-01-01

We investigated the effect of overexpressing a pumpkin gibberellin (GA) 20-oxidase gene encoding an enzyme that forms predominantly biologically inactive products on GA biosynthesis and plant morphology in transgenic lettuce (Lactuca sativa cv Vanguard) plants. Lettuce was transformed with the pumpkin GA 20-oxidase gene downstream of a strong constitutive promoter cassette (El2–35S-Ω). The transgenic plants in which the pumpkin gene was detected by polymerase chain reaction were dwarfed in the T2 generation, whereas transformants with a normal growth phenotype did not contain the transgene. The result of Southern-blot analysis showed that the transgene was integrated as a single copy; the plants segregated three dwarfs to one normal in the T2 generation, indicating that the transgene was stable and dominant. The endogenous levels of GA1 and GA4 were reduced in the dwarfs, whereas large amounts of GA17 and GA25, which are inactive products of the pumpkin GA 20-oxidase, accumulated in these lines. These results indicate that a functional pumpkin GA 20-oxidase is expressed in the transgenic lettuce, resulting in a diversion of the normal pathway of GA biosynthesis to inactive products. Furthermore, this technique may be useful for controlling plant stature in other agricultural and horticultural species. PMID:11457947

A Gibberellin-Mediated DELLA-NAC Signaling Cascade Regulates Cellulose Synthesis in Rice.

PubMed

Huang, Debao; Wang, Shaogan; Zhang, Baocai; Shang-Guan, Keke; Shi, Yanyun; Zhang, Dongmei; Liu, Xiangling; Wu, Kun; Xu, Zuopeng; Fu, Xiangdong; Zhou, Yihua

2015-06-01

Cellulose, which can be converted into numerous industrial products, has important impacts on the global economy. It has long been known that cellulose synthesis in plants is tightly regulated by various phytohormones. However, the underlying mechanism of cellulose synthesis regulation remains elusive. Here, we show that in rice (Oryza sativa), gibberellin (GA) signals promote cellulose synthesis by relieving the interaction between SLENDER RICE1 (SLR1), a DELLA repressor of GA signaling, and NACs, the top-layer transcription factors for secondary wall formation. Mutations in GA-related genes and physiological treatments altered the transcription of CELLULOSE SYNTHASE genes (CESAs) and the cellulose level. Multiple experiments demonstrated that transcription factors NAC29/31 and MYB61 are CESA regulators in rice; NAC29/31 directly regulates MYB61, which in turn activates CESA expression. This hierarchical regulation pathway is blocked by SLR1-NAC29/31 interactions. Based on the results of anatomical analysis and GA content examination in developing rice internodes, this signaling cascade was found to be modulated by varied endogenous GA levels and to be required for internode development. Genetic and gene expression analyses were further performed in Arabidopsis thaliana GA-related mutants. Altogether, our findings reveal a conserved mechanism by which GA regulates secondary wall cellulose synthesis in land plants and provide a strategy for manipulating cellulose production and plant growth. © 2015 American Society of Plant Biologists. All rights reserved.

A Gibberellin-Mediated DELLA-NAC Signaling Cascade Regulates Cellulose Synthesis in Rice[OPEN

PubMed Central

Huang, Debao; Wang, Shaogan; Zhang, Baocai; Shang-Guan, Keke; Shi, Yanyun; Zhang, Dongmei; Liu, Xiangling; Wu, Kun; Xu, Zuopeng; Fu, Xiangdong; Zhou, Yihua

2015-01-01

Cellulose, which can be converted into numerous industrial products, has important impacts on the global economy. It has long been known that cellulose synthesis in plants is tightly regulated by various phytohormones. However, the underlying mechanism of cellulose synthesis regulation remains elusive. Here, we show that in rice (Oryza sativa), gibberellin (GA) signals promote cellulose synthesis by relieving the interaction between SLENDER RICE1 (SLR1), a DELLA repressor of GA signaling, and NACs, the top-layer transcription factors for secondary wall formation. Mutations in GA-related genes and physiological treatments altered the transcription of CELLULOSE SYNTHASE genes (CESAs) and the cellulose level. Multiple experiments demonstrated that transcription factors NAC29/31 and MYB61 are CESA regulators in rice; NAC29/31 directly regulates MYB61, which in turn activates CESA expression. This hierarchical regulation pathway is blocked by SLR1-NAC29/31 interactions. Based on the results of anatomical analysis and GA content examination in developing rice internodes, this signaling cascade was found to be modulated by varied endogenous GA levels and to be required for internode development. Genetic and gene expression analyses were further performed in Arabidopsis thaliana GA-related mutants. Altogether, our findings reveal a conserved mechanism by which GA regulates secondary wall cellulose synthesis in land plants and provide a strategy for manipulating cellulose production and plant growth. PMID:26002868

A Novel Class of Gibberellin 2-Oxidases Control Semidwarfism, Tillering, and Root Development in Rice[W

PubMed Central

Lo, Shuen-Fang; Yang, Show-Ya; Chen, Ku-Ting; Hsing, Yue-Ie; Zeevaart, Jan A.D.; Chen, Liang-Jwu; Yu, Su-May

2008-01-01

Gibberellin 2-oxidases (GA2oxs) regulate plant growth by inactivating endogenous bioactive gibberellins (GAs). Two classes of GA2oxs inactivate GAs through 2β-hydroxylation: a larger class of C19 GA2oxs and a smaller class of C20 GA2oxs. In this study, we show that members of the rice (Oryza sativa) GA2ox family are differentially regulated and act in concert or individually to control GA levels during flowering, tillering, and seed germination. Using mutant and transgenic analysis, C20 GA2oxs were shown to play pleiotropic roles regulating rice growth and architecture. In particular, rice overexpressing these GA2oxs exhibited early and increased tillering and adventitious root growth. GA negatively regulated expression of two transcription factors, O. sativa homeobox 1 and TEOSINTE BRANCHED1, which control meristem initiation and axillary bud outgrowth, respectively, and that in turn inhibited tillering. One of three conserved motifs unique to the C20 GA2oxs (motif III) was found to be important for activity of these GA2oxs. Moreover, C20 GA2oxs were found to cause less severe GA-defective phenotypes than C19 GA2oxs. Our studies demonstrate that improvements in plant architecture, such as semidwarfism, increased root systems and higher tiller numbers, could be induced by overexpression of wild-type or modified C20 GA2oxs. PMID:18952778

[Change of endogenous hormone around sprout tumble of Pinellia ternata under high temperature stress].

PubMed

Xue, Jian-Ping; Zhang, Ai-Min; Yang, Jian; Chang, Li; Huang, Yue-Qin

2007-12-01

To study the change of endogenous hormone (ABA, IAA, JA, GA3, ZR) in the leaves, petioles, tubers of Pinellia ternate around sprout tumble. It also provided some valuable information to prevent sprout tumble and increase production. Tubers of P. ternata were cultured firstly at (23 +/- 1) degree C for certain days, and then they were coerced under (30 +/- 1 ) degree C stress in the same artificial climate boxes. The endogenous hormones in leaves, petioles and tubers during different stages of high temperature stress were determined with Enzyme-linked Immunosorbent Assays (ELISA). After under high temperature stress, ABA content in leaves, petioles and tubers increased obviously. Similarly, JA content rose all in the leaves, petioles and tubers. But in the same conditions IAA content declined significantly in the leaves and petioles. In the tubers, IAA content also decreased, but not quickly. With the extension of high temperature coercion, the leaves, petioles, tubers, ZR content were gradually falling off. In the leaves of GA3 content rose markedly at the third day, fell down at the sixth day, but remained higher than before treatment. With the extension of the processing time, GA3 content fell off in the petioles and tubers. ABA, JA, ZT and GA3 played an important role in controlling sprout tumble of P. ternata.

A local maximum in gibberellin levels regulates maize leaf growth by spatial control of cell division.

PubMed

Nelissen, Hilde; Rymen, Bart; Jikumaru, Yusuke; Demuynck, Kirin; Van Lijsebettens, Mieke; Kamiya, Yuji; Inzé, Dirk; Beemster, Gerrit T S

2012-07-10

Plant growth rate is largely determined by the transition between the successive phases of cell division and expansion. A key role for hormone signaling in determining this transition was inferred from genetic approaches and transcriptome analysis in the Arabidopsis root tip. We used the developmental gradient at the maize leaf base as a model to study this transition, because it allows a direct comparison between endogenous hormone concentrations and the transitions between dividing, expanding, and mature tissue. Concentrations of auxin and cytokinins are highest in dividing tissues, whereas bioactive gibberellins (GAs) show a peak at the transition zone between the division and expansion zone. Combined metabolic and transcriptomic profiling revealed that this GA maximum is established by GA biosynthesis in the division zone (DZ) and active GA catabolism at the onset of the expansion zone. Mutants defective in GA synthesis and signaling, and transgenic plants overproducing GAs, demonstrate that altering GA levels specifically affects the size of the DZ, resulting in proportional changes in organ growth rates. This work thereby provides a novel molecular mechanism for the regulation of the transition from cell division to expansion that controls organ growth and size. Copyright © 2012 Elsevier Ltd. All rights reserved.

Gibberellins Are Required for Seed Development and Pollen Tube Growth in Arabidopsis

PubMed Central

Singh, Davinder P.; Jermakow, Angelica M.; Swain, Stephen M.

2002-01-01

Gibberellins (GAs) are tetracyclic diterpenoids that are essential endogenous regulators of plant growth and development. GA levels within the plant are regulated by a homeostatic mechanism that includes changes in the expression of a family of GA-inactivating enzymes known as GA 2-oxidases. Ectopic expression of a pea GA 2-oxidase2 cDNA caused seed abortion in Arabidopsis, extending and confirming previous observations obtained with GA-deficient mutants of pea, suggesting that GAs have an essential role in seed development. A new physiological role for GAs in pollen tube growth in vivo also has been identified. The growth of pollen tubes carrying the 35S:2ox2 transgene was reduced relative to that of nontransgenic pollen, and this phenotype could be reversed partially by GA application in vitro or by combining with spy-5, a mutation that increases GA response. Treatment of wild-type pollen tubes with an inhibitor of GA biosynthesis in vitro also suggested that GAs are required for normal pollen tube growth. These results extend the known physiological roles of GAs in Arabidopsis development and suggest that GAs are required for normal pollen tube growth, a physiological role for GAs that has not been established previously. PMID:12468732

Green revolution trees: semidwarfism transgenes modify gibberellins, promote root growth, enhance morphological diversity, and reduce competitiveness in hybrid poplar.

PubMed

Elias, Ani A; Busov, Victor B; Kosola, Kevin R; Ma, Cathleen; Etherington, Elizabeth; Shevchenko, Olga; Gandhi, Harish; Pearce, David W; Rood, Stewart B; Strauss, Steven H

2012-10-01

Semidwarfism has been used extensively in row crops and horticulture to promote yield, reduce lodging, and improve harvest index, and it might have similar benefits for trees for short-rotation forestry or energy plantations, reclamation, phytoremediation, or other applications. We studied the effects of the dominant semidwarfism transgenes GA Insensitive (GAI) and Repressor of GAI-Like, which affect gibberellin (GA) action, and the GA catabolic gene, GA 2-oxidase, in nursery beds and in 2-year-old high-density stands of hybrid poplar (Populus tremula × Populus alba). Twenty-nine traits were analyzed, including measures of growth, morphology, and physiology. Endogenous GA levels were modified in most transgenic events; GA(20) and GA(8), in particular, had strong inverse associations with tree height. Nearly all measured traits varied significantly among genotypes, and several traits interacted with planting density, including aboveground biomass, root-shoot ratio, root fraction, branch angle, and crown depth. Semidwarfism promoted biomass allocation to roots over shoots and substantially increased rooting efficiency with most genes tested. The increased root proportion and increased leaf chlorophyll levels were associated with changes in leaf carbon isotope discrimination, indicating altered water use efficiency. Semidwarf trees had dramatically reduced growth when in direct competition with wild-type trees, supporting the hypothesis that semidwarfism genes could be effective tools to mitigate the spread of exotic, hybrid, and transgenic plants in wild and feral populations.

Green Revolution Trees: Semidwarfism Transgenes Modify Gibberellins, Promote Root Growth, Enhance Morphological Diversity, and Reduce Competitiveness in Hybrid Poplar1[C][W][OA

PubMed Central

Elias, Ani A.; Busov, Victor B.; Kosola, Kevin R.; Ma, Cathleen; Etherington, Elizabeth; Shevchenko, Olga; Gandhi, Harish; Pearce, David W.; Rood, Stewart B.; Strauss, Steven H.

2012-01-01

Semidwarfism has been used extensively in row crops and horticulture to promote yield, reduce lodging, and improve harvest index, and it might have similar benefits for trees for short-rotation forestry or energy plantations, reclamation, phytoremediation, or other applications. We studied the effects of the dominant semidwarfism transgenes GA Insensitive (GAI) and Repressor of GAI-Like, which affect gibberellin (GA) action, and the GA catabolic gene, GA 2-oxidase, in nursery beds and in 2-year-old high-density stands of hybrid poplar (Populus tremula × Populus alba). Twenty-nine traits were analyzed, including measures of growth, morphology, and physiology. Endogenous GA levels were modified in most transgenic events; GA20 and GA8, in particular, had strong inverse associations with tree height. Nearly all measured traits varied significantly among genotypes, and several traits interacted with planting density, including aboveground biomass, root-shoot ratio, root fraction, branch angle, and crown depth. Semidwarfism promoted biomass allocation to roots over shoots and substantially increased rooting efficiency with most genes tested. The increased root proportion and increased leaf chlorophyll levels were associated with changes in leaf carbon isotope discrimination, indicating altered water use efficiency. Semidwarf trees had dramatically reduced growth when in direct competition with wild-type trees, supporting the hypothesis that semidwarfism genes could be effective tools to mitigate the spread of exotic, hybrid, and transgenic plants in wild and feral populations. PMID:22904164

Effect of proline on biochemical and molecular mechanisms in lettuce (Lactuca sativa L.) exposed to UV-B radiation.

PubMed

Aksakal, Ozkan; Tabay, Dilruba; Esringu, Aslıhan; Icoglu Aksakal, Feyza; Esim, Nevzat

2017-02-15

The purpose of the present study was to evaluate the role of proline (Pro) in relieving UV-B radiation-induced oxidative stress in lettuce. Lettuce seedlings were exposed to 3.3 W m -2 UV-B radiation for 12 h after pre-treatment sprayed with 20 mM Pro. The data for malondialdehyde (MDA), hydrogen peroxide (H 2 O 2 ), endogenous Pro level, the activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD)], total phenolic concentration, antioxidant capacity, expression of phenylalanine ammonia lyase (PAL), γ-tocopherol methyltransferase (γ-TMT) and proline dehydrogenase (ProDH) genes, phytohormone levels such as abscisic acid (ABA), gibberellic acid (GA), indole acetic acid (IAA) and salicylic acid (SA), soluble sugars and organic acids were recorded. It was found that Pro alleviated the oxidative damage in the seedlings of lettuce as demonstrated by lower lipid peroxidation and H 2 O 2 content, increasing the endogenous Pro level, the activity of antioxidant enzymes, total phenolic concentration and the antioxidant capacity. Additionally, it was revealed that exogenous application of Pro enhanced the levels of GA, IAA, the concentrations of soluble sugars and organic acids and expressions of PAL, γ-TMT and ProDH genes as compared to the control. The results obtained in this study suggest that pre-treatment with exogenous Pro provides important contributions to the increase in the UV-B tolerance of lettuce by regulating the biochemical mechanisms of UV-B response.

OsWOX3A is involved in negative feedback regulation of the gibberellic acid biosynthetic pathway in rice (Oryza sativa).

PubMed

Cho, Sung-Hwan; Kang, Kiyoon; Lee, Sang-Hwa; Lee, In-Jung; Paek, Nam-Chon

2016-03-01

The plant-specific WUSCHEL-related homeobox (WOX) nuclear proteins have important roles in the transcriptional regulation of many developmental processes. Among the rice (Oryza sativa) WOX proteins, a loss of OsWOX3A function in narrow leaf2 (nal2) nal3 double mutants (termed nal2/3) causes pleiotropic effects, such as narrow and curly leaves, opened spikelets, narrow grains, more tillers, and fewer lateral roots, but almost normal plant height. To examine OsWOX3A function in more detail, transgenic rice overexpressing OsWOX3A (OsWOX3A-OX) were generated; unexpectedly, all of them consistently exhibited severe dwarfism with very short and wide leaves, a phenotype that resembles that of gibberellic acid (GA)-deficient or GA-insensitive mutants. Exogenous GA3 treatment fully rescued the developmental defects of OsWOX3A-OX plants, suggesting that constitutive overexpression of OsWOX3A downregulates GA biosynthesis. Quantitative analysis of GA intermediates revealed significantly reduced levels of GA20 and bioactive GA1 in OsWOX3A-OX, possibly due to downregulation of the expression of KAO, which encodes ent-kaurenoic acid oxidase, a GA biosynthetic enzyme. Yeast one-hybrid and electrophoretic mobility shift assays revealed that OsWOX3A directly interacts with the KAO promoter. OsWOX3A expression is drastically and temporarily upregulated by GA3 and downregulated by paclobutrazol, a blocker of GA biosynthesis. These data indicate that OsWOX3A is a GA-responsive gene and functions in the negative feedback regulation of the GA biosynthetic pathway for GA homeostasis to maintain the threshold levels of endogenous GA intermediates throughout development. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Radioprotective Effects of Gallic Acid in Mice

PubMed Central

Nair, Gopakumar Gopinathan

2013-01-01

Radioprotecting ability of the natural polyphenol, gallic acid (3,4,5-trihydroxybenzoic acid, GA), was investigated in Swiss albino mice. Oral administration of GA (100 mg/kg body weight), one hour prior to whole body gamma radiation exposure (2–8 Gy; 6 animals/group), reduced the radiation-induced cellular DNA damage in mouse peripheral blood leukocytes, bone marrow cells, and spleenocytes as revealed by comet assay. The GA administration also prevented the radiation-induced decrease in the levels of the antioxidant enzyme, glutathione peroxidise (GPx), and nonprotein thiol glutathione (GSH) and inhibited the peroxidation of membrane lipids in these animals. Exposure of mice to whole body gamma radiation also caused the formation of micronuclei in blood reticulocytes and chromosomal aberrations in bone marrow cells, and the administration of GA resulted in the inhibition of micronucleus formation and chromosomal aberrations. In irradiated animals, administration of GA elicited an enhancement in the rate of DNA repair process and a significant increase in endogenous spleen colony formation. The administration of GA also prevented the radiation-induced weight loss and mortality in animals (10 animals/group) exposed to lethal dose (10 Gy) of gamma radiation. (For every experiment unirradiated animals without GA administration were taken as normal control; specific dose (Gy) irradiated animals without GA administration serve as radiation control; and unirradiated GA treated animals were taken as drug alone control). PMID:24069607

Abscisic acid regulates seed germination of Vellozia species in response to temperature.

PubMed

Vieira, B C; Bicalho, E M; Munné-Bosch, S; Garcia, Q S

2017-03-01

The relationship between the phytohormones, gibberellin (GA) and abscisic acid (ABA) and light and temperature on seed germination is still not well understood. We aimed to investigate the role of the ABA and GA on seed germination of Vellozia caruncularis, V. intermedia and V. alutacea in response to light/dark conditions on different temperature. Seeds were incubated in GA (GA 3 or GA 4 ) or ABA and their respective biosynthesis inhibitors (paclobutrazol - PAC, and fluridone - FLU) solutions at two contrasting temperatures (25 and 40 °C). Furthermore, endogenous concentrations of active GAs and those of ABA were measured in seeds of V. intermedia and V. alutacea during imbibition/germination. Exogenous ABA inhibited the germination of Vellozia species under all conditions tested. GA, FLU and FLU + GA 3 stimulated germination in the dark at 25 °C (GA 4 being more effective than GA 3 ). PAC reduced seed germination in V. caruncularis and V. alutacea, but did not affect germination of V. intermedia at 40 °C either under light or dark conditions. During imbibition in the dark, levels of active GAs decreased in the seeds of V. intermedia, but were not altered in those of V. alutacea. Incubation at 40 °C decreased ABA levels during imbibition in both V. caruncularis and V. alutacea. We conclude that the seeds of Vellozia species studied here require light or high temperature to germinate and ABA has a major role in the regulation of Vellozia seed germination in response to light and temperature. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

Heterosis in Rice Seedlings: Its Relationship to Gibberellin Content and Expression of Gibberellin Metabolism and Signaling Genes1[W][OA

PubMed Central

Ma (马谦), Qian; Hedden, Peter; Zhang (张启发), Qifa

2011-01-01

Despite the accumulation of data on the genetic and molecular understanding of heterosis, there is little information on the regulation of heterosis at the physiological level. In this study, we performed a quantitative analysis of endogenous gibberellin (GA) content and expression profiling of the GA metabolism and signaling genes to investigate the possible relationship between GA signaling and heterosis for seedling development in rice (Oryza sativa). The materials used were an incomplete diallele set of 3 × 3 crosses and the six parents. In the growing shoots of the seedlings at 20 d after sowing, significant positive correlations between the contents of some GA species and performance and heterosis based on shoot dry mass were detected. Expression analyses of GA-related genes by real-time reverse transcription-polymerase chain reaction revealed that 13 out of the 16 GA-related genes examined exhibited significant differential expression among the F1 hybrid and its parents, acting predominantly in the modes of overdominance and positive dominance. Expression levels of nine genes in the hybrids displayed significant positive correlations with the heterosis of shoot dry mass. These results imply that GAs play a positive role in the regulation of heterosis for rice seedling development. In shoots plus root axes of 4-d-old germinating seeds that had undergone the deetiolation, mimicking normal germination in soil, the axis dry mass was positively correlated with the content of GA29 but negatively correlated with that of GA19. Our findings provide supporting evidence for GAs playing an important regulatory role in heterosis for rice seedling development. PMID:21693671

Epigenetic and physiological effects of gibberellin inhibitors and chemical pruners on the floral transition of azalea.

PubMed

Meijón, Mónica; Cañal, María Jesús; Valledor, Luis; Rodríguez, Roberto; Feito, Isabel

2011-03-01

The ability to control the timing of flowering is a key strategy in planning the production of ornamental species such as azaleas; however, it requires a thorough understanding of floral transition. DNA methylation is involved in controlling the functional state of chromatin and gene expression during floral induction pathways in response to environmental and developmental signals. Plant hormone signalling is also known to regulate suites of morphogenic processes in plants and its role in flowering-time control is starting to emerge as a key controlling step. This work investigates if the gibberellin (GA) inhibitors and chemical pinching applied in improvement of azalea flowering alter the dynamics of DNA methylation or the levels of polyamines (PAs), GAs and cytokinins (CKs) during floral transition, and whether these changes could be related to the effects observed on flowering ability. DNA methylation during floral transition and endogenous content of PAs, GAs and CKs were analysed after the application of GA synthesis inhibitors (daminozide, paclobutrazol and chlormequat chloride) and a chemical pruner (fatty acids). The application of GA biosynthesis inhibitors caused alterations in levels of PAs, GAs and CKs and in global DNA methylation levels during floral transition; also, these changes in plant growth regulators and DNA methylation were correlated with flower development. DNA methylation, PA, GA and CK levels can be used as predictive markers of plant floral capacity in azalea. Copyright © Physiologia Plantarum 2010.

Dormancy in Peach (Prunus persica L.) Flower Buds : I. Floral Morphogenesis and Endogenous Gibberellins at the End of the Dormancy Period.

PubMed

Luna, V; Lorenzo, E; Reinoso, H; Tordable, M C; Abdala, G; Pharis, R P; Bottini, R

1990-05-01

Flower buds of peach (Prunus persica L.) trees, cv Novedad de Cordoba (Argentina), were collected near the end of the dormant period and immediately before anthesis. After removal of scale leaves, morphological observations of representative buds, made on transverse and longitudinal microtome sections, showed that all verticils making up the flower are present in an undifferentiated form during the dormant period (June). Flower buds collected at the end of dormant period (August) showed additional growth and differentiation, at which time formation of two ovules was beginning in the unicarpelar gynoecium. Dehiscence of anthers had not yet occurred 10 days before full bloom, and the ovules were still developing. Free endogenous gibberellin (GA)-like substances were quantified by bioassay (Tan-ginbozu dwarf rice microdrop) after SiO(2) partition column chromatography, reversed phase C18-high performance liquid chromatography, and finally Nucleosil [N(CH(3))(2)]high performance liquid chromatography. Bioactive fractions were then subjected to capillary gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM). Gibberellins A(1), A(3), and A(8) were tentatively identified in peach flower buds using GC-SIM and Kovat's retention indices, and relative amounts approximated by GC-SIM (2:8:6 for GA(1), GA(3), and GA(8), respectively). The highest concentration (330 nanograms per gram dry weight) of free GA(1)/GA(3) was found in dormant buds (June) and diminished thereafter. The concentration free of GA(1)/GA(3) did not increase immediately prior to bud break. However, high GA(1)/GA(3) concentrations occurred during stages where rate of growth and cellular differentiation of (mainly fertile) verticils can be influenced.

Phenotypic plasticity of sun and shade ecotypes of Stellaria longipes in response to light quality signaling, gibberellins and auxin.

PubMed

Kurepin, Leonid V; Pharis, Richard P; Neil Emery, R J; Reid, David M; Chinnappa, C C

2015-09-01

Stellaria longipes plant communities (ecotypes) occur in several environmentally distinct habitats along the eastern slopes of southern Alberta's Rocky Mountains. One ecotype occurs in a prairie habitat at ∼1000 m elevation where Stellaria plants grow in an environment in which the light is filtered by taller neighbouring vegetation, i.e. sunlight with a low red to far-red (R/FR) ratio. This ecotype exhibits a high degree of phenotypic plasticity by increasing stem elongation in response to the low R/FR ratio light signal. Another Stellaria ecotype occurs nearby at ∼2400 m elevation in a much cooler alpine habitat, one where plants rarely experience low R/FR ratio shade light. Stem elongation of plants is largely regulated by gibberellins (GAs) and auxin, indole-3-acetic acid (IAA). Shoots of the prairie ecotype plants show increased IAA levels under low R/FR ratio light and they also increase their stem growth in response to applied IAA. The alpine ecotype plants show neither response. Plants from both ecotypes produce high levels of growth-active GA1 under low R/FR ratio light, though they differ appreciably in their catabolism of GA1. The alpine ecotype plants exhibit very high levels of GA8, the inactive product of GA1 metabolism, under both normal and low R/FR ratio light. Alpine origin plants may de-activate GA1 by conversion to GA8 via a constitutively high level of expression of the GA2ox gene, thereby maintaining their dwarf phenotype and exhibiting a reduced phenotypic plasticity in terms of shoot elongation. In contrast, prairie plants exhibit a high degree of phenotypic plasticity, using low R/FR ratio light-mediated changes in GA and IAA concentrations to increase shoot elongation, thereby accessing direct sunlight to optimize photosynthesis. There thus appear to be complex adaptation strategies for the two ecotypes, ones which involve modifications in the homeostasis of endogenous hormones. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Heterosis in rice seedlings: its relationship to gibberellin content and expression of gibberellin metabolism and signaling genes.

PubMed

Ma, Qian; Hedden, Peter; Zhang, Qifa

2011-08-01

Despite the accumulation of data on the genetic and molecular understanding of heterosis, there is little information on the regulation of heterosis at the physiological level. In this study, we performed a quantitative analysis of endogenous gibberellin (GA) content and expression profiling of the GA metabolism and signaling genes to investigate the possible relationship between GA signaling and heterosis for seedling development in rice (Oryza sativa). The materials used were an incomplete diallele set of 3 × 3 crosses and the six parents. In the growing shoots of the seedlings at 20 d after sowing, significant positive correlations between the contents of some GA species and performance and heterosis based on shoot dry mass were detected. Expression analyses of GA-related genes by real-time reverse transcription-polymerase chain reaction revealed that 13 out of the 16 GA-related genes examined exhibited significant differential expression among the F1 hybrid and its parents, acting predominantly in the modes of overdominance and positive dominance. Expression levels of nine genes in the hybrids displayed significant positive correlations with the heterosis of shoot dry mass. These results imply that GAs play a positive role in the regulation of heterosis for rice seedling development. In shoots plus root axes of 4-d-old germinating seeds that had undergone the deetiolation, mimicking normal germination in soil, the axis dry mass was positively correlated with the content of GA₂₉ but negatively correlated with that of GA₁₉. Our findings provide supporting evidence for GAs playing an important regulatory role in heterosis for rice seedling development.

The endogenous hormones in soybean seedlings under the joint actions of rare earth element La(III) and ultraviolet-B stress.

PubMed

Peng, Qi; Zhou, Qing

2009-12-01

The dynamic state of endogenous hormone content in soybean seedlings was investigated for a further demonstration of alleviating the damage of the ultraviolet ultraviolet-B (UV-B) radiation in the La(III)-treated soybean seedlings under UV-B stress. Using hydroponics culture, the effects of lanthanum(III) on the contents of endogenous hormone under elevated ultraviolet-B radiation (280–320 nm) was studied. The results showed that the content of indole-3-acetic acid (IAA) in soybean seedlings decreased initially and then increased when the seedlings underwent UV-B treatment during the stress and convalescent period; this was compared with a control; acetic acid oxidase (IAAO) activity increased at first (first to fifth day) and then decreased (sixth to 11th day). A similar change of abscisic acid content and IAAO content in soybean seedlings occurred; gibberellic acid (GA) content decreased during the experiment compared with control. The content of IAA and GA in soybean seedlings with La(III) + UV-B treatment was higher than those of UV-B treatment; IAAO activity and GA content in soybean seedlings with La (III) + UV-B treatment were lower than those of UV-B treatment. It suggested that the regulative effect of La(III) at the optimum concentration on endogenous hormone improved the ability of plant stress resistance, and its protective effect against low UV-B radiation was superior to high UV-B radiation. The defensive effect of La(III) on soybean seedlings under UV-B stress was carried out on the layer of defense system.

Transport and Metabolism of 3H-Gibberellin A1 in Dioecious Cucumber Seedlings 1

PubMed Central

Rudich, Jehoshua; Sell, Harold M.; Baker, Larry R.

1976-01-01

The transport of 3H-GA1 through hypocotyl segments of cucumber (Cucumis sativus L.) was found to be nonpolar. The transport of 3H-GA1 was increased by pretreatment with relatively high concentrations of either IAA or Ethephon (2-chloroethylphosphonic acid). Hypocotyl segments from plants of a gynoecious genotype transported more 3H-GA1 than those of an androecious. The metabolism of 3H-GA1 in hypocotyl segments was neither related to the sex genotype of the cucumber plant nor influenced by pretreatment with Ethephon. The primary metabolite of GA1 was suggested to be GA8. Two other suspected metabolites were not identified. Differences in the endogenous GA of gynoecious and androecious plants could not be accounted for by transport differences. PMID:16659561

Gibberellin reactivates and maintains ovary-wall cell division causing fruit set in parthenocarpic Citrus species.

PubMed

Mesejo, Carlos; Yuste, Roberto; Reig, Carmina; Martínez-Fuentes, Amparo; Iglesias, Domingo J; Muñoz-Fambuena, Natalia; Bermejo, Almudena; Germanà, M Antonietta; Primo-Millo, Eduardo; Agustí, Manuel

2016-06-01

Citrus is a wide genus in which most of the cultivated species and cultivars are natural parthenocarpic mutants or hybrids (i.e. orange, mandarin, tangerine, grapefruit). The autonomous increase in GA1 ovary concentration during anthesis was suggested as being the stimulus responsible for parthenocarpy in Citrus regardless of the species. To determine the exact GA-role in parthenocarpic fruit set, the following hypothesis was tested: GA triggers and maintains cell division in ovary walls causing fruit set. Obligate and facultative parthenocarpic Citrus species were used as a model system because obligate parthenocarpic Citrus sp (i.e. Citrus unshiu) have higher GA levels and better natural parthenocarpic fruit set compared to other facultative parthenocarpic Citrus (i.e. Citrus clementina). The autonomous activation of GA synthesis in C. unshiu ovary preceded cell division and CYCA1.1 up-regulation (a G2-stage cell cycle regulator) at anthesis setting a high proportion of fruits, whereas C. clementina lacked this GA-biosynthesis and CYCA1.1 up-regulation failing in fruit set. In situ hybridization experiments revealed a tissue-specific expression of GA20ox2 only in the dividing tissues of the pericarp. Furthermore, CYCA1.1 expression correlated endogenous GA1 content with GA3 treatment, which stimulated cell division and ovary growth, mostly in C. clementina. Instead, paclobutrazol (GA biosynthesis inhibitor) negated cell division and reduced fruit set. Results suggest that in parthenocarpic citrus the specific GA synthesis in the ovary walls at anthesis triggers cell division and, thus, the necessary ovary growth rate to set fruit. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Salicylic acid-related cotton (Gossypium arboreum) ribosomal protein GaRPL18 contributes to resistance to Verticillium dahliae.

PubMed

Gong, Qian; Yang, Zhaoen; Wang, Xiaoqian; Butt, Hamama Islam; Chen, Eryong; He, Shoupu; Zhang, Chaojun; Zhang, Xueyan; Li, Fuguang

2017-03-03

Verticillium dahliae is a phytopathogenic fungal pathogen that causes vascular wilt diseases responsible for considerable decreases in cotton yields. The complex mechanism underlying cotton resistance to Verticillium wilt remains uncharacterized. Identifying an endogenous resistance gene may be useful for controlling this disease. We cloned the ribosomal protein L18 (GaRPL18) gene, which mediates resistance to Verticillium wilt, from a wilt-resistant cotton species (Gossypium arboreum). We then characterized the function of this gene in cotton and Arabidopsis thaliana plants. GaRPL18 encodes a 60S ribosomal protein subunit important for intracellular protein biosynthesis. However, previous studies revealed that some ribosomal proteins are also inhibitory toward oncogenesis and congenital diseases in humans and play a role in plant disease defense. Here, we observed that V. dahliae infections induce GaRPL18 expression. Furthermore, we determined that the GaRPL18 expression pattern is consistent with the disease resistance level of different cotton varieties. GaRPL18 expression is upregulated by salicylic acid (SA) treatments, suggesting the involvement of GaRPL18 in the SA signal transduction pathway. Virus-induced gene silencing technology was used to determine whether the GaRPL18 expression level influences cotton disease resistance. Wilt-resistant cotton species in which GaRPL18 was silenced became more susceptible to V. dahliae than the control plants because of a significant decrease in the abundance of immune-related molecules. We also transformed A. thaliana ecotype Columbia (Col-0) plants with GaRPL18 according to the floral dip method. The plants overexpressing GaRPL18 were more resistant to V. dahliae infections than the wild-type Col-0 plants. The enhanced resistance of transgenic A. thaliana plants to V. dahliae is likely mediated by the SA pathway. Our findings provide new insights into the role of GaRPL18, indicating that it plays a crucial role in resistance to cotton "cancer", also known as Verticillium wilt, mainly regulated by an SA-related signaling pathway mechanism.

Phytochrome Regulates Gibberellin Biosynthesis during Germination of Photoblastic Lettuce Seeds1

PubMed Central

Toyomasu, Tomonobu; Kawaide, Hiroshi; Mitsuhashi, Wataru; Inoue, Yasunori; Kamiya, Yuji

1998-01-01

Germination of lettuce (Lactuca sativa L.) seed is regulated by phytochrome. The requirement for red light is circumvented by the application of gibberellin (GA). We have previously shown that the endogenous content of GA1, the main bioactive GA in lettuce seeds, increases after red-light treatment. To clarify which step of GA1 synthesis is regulated by phytochrome, cDNAs encoding GA 20-oxidases (Ls20ox1 and Ls20ox2, for L. sativa GA 20-oxidase) and 3β-hydroxylases (Ls3h1 and Ls3h2 for L. sativa GA 3β-hydroxylase) were isolated from lettuce seeds by reverse-transcription polymerase chain reaction. Functional analysis of recombinant proteins expressed in Escherichia coli confirmed that the Ls20ox and Ls3h encode GA 20-oxidases and 3β-hydroxylases, respectively. Northern-blot analysis showed that Ls3h1 expression was dramatically induced by red-light treatment within 2 h, and that this effect was canceled by a subsequent far-red-light treatment. Ls3h2 mRNA was not detected in seeds that had been allowed to imbibe under any light conditions. Expression of the two Ls20ox genes was induced by initial imbibition alone in the dark. The level of Ls20ox2 mRNA decreased after the red-light treatment, whereas that of Ls20ox1 was unaffected by light. These results suggest that red light promotes GA1 synthesis in lettuce seeds by inducing Ls3h1 expression via phytochrome action. PMID:9847128

On the Problem of Patient-Specific Endogenous Glucose Production in Neonates on Stochastic Targeted Glycemic Control

PubMed Central

Dickson, Jennifer L.; Hewett, James N.; Gunn, Cameron A.; Lynn, Adrienne; Shaw, Geoffrey M.; Chase, Geoffrey

2013-01-01

Background: Both stress and prematurity can induce hyperglycemia in the neonatal intensive care unit, which, in turn, is associated with worsened outcomes. Endogenous glucose production (EGP) is the formation of glucose by the body from substrates and contributes to blood glucose (BG) levels. Due to the inherent fragility of the extremely low birth weight (ELBW) neonates, true fasting EGP cannot be explicitly determined, introducing uncertainty into glycemic models that rely on quantifying glucose sources. Stochastic targeting, or STAR, is one such glycemic control framework. Methods: A literature review was carried out to gather metabolic and EGP values on preterm infants with a gestational age (GA) <32 weeks and a birth weight (BW) <2 kg. The data were analyzed for EGP trends with BW, GA, BG, plasma insulin, and glucose infusion (GI) rates. Trends were modeled and compared with a literature-derived range of population constant EGP models using clinically validated virtual trials on retrospective clinical data. Results: No clear relationship was found for EGP and BW, GA, or plasma insulin. Some evidence of suppression of EGP with increasing GI or BG was seen. Virtual trial results showed that population-constant EGP models fit clinical data best and gave tighter control performance to a target band in virtual trials. Conclusions: Variation in EGP cannot easily be quantified, and EGP is sufficiently modeled as a population constant in the neonatal intensive care insulin–nutrition–glucose model. Analysis of the clinical data and fitting error suggests that ELBW hyperglycemic preterm neonates have unsuppressed EGP in the higher range than that seen in literature. PMID:23911173

Reactivation of meristem activity and sprout growth in potato tubers require both cytokinin and gibberellin.

PubMed

Hartmann, Anja; Senning, Melanie; Hedden, Peter; Sonnewald, Uwe; Sonnewald, Sophia

2011-02-01

Reactivation of dormant meristems is of central importance for plant fitness and survival. Due to their large meristem size, potato (Solanum tuberosum) tubers serve as a model system to study the underlying molecular processes. The phytohormones cytokinins (CK) and gibberellins (GA) play important roles in releasing potato tuber dormancy and promoting sprouting, but their mode of action in these processes is still obscure. Here, we established an in vitro assay using excised tuber buds to study the dormancy-releasing capacity of GA and CK and show that application of gibberellic acid (GA(3)) is sufficient to induce sprouting. In contrast, treatment with 6-benzylaminopurine induced bud break but did not support further sprout growth unless GA(3) was administered additionally. Transgenic potato plants expressing Arabidopsis (Arabidopsis thaliana) GA 20-oxidase or GA 2-oxidase to modify endogenous GA levels showed the expected phenotypical changes as well as slight effects on tuber sprouting. The isopentenyltransferase (IPT) from Agrobacterium tumefaciens and the Arabidopsis cytokinin oxidase/dehydrogenase1 (CKX) were exploited to modify the amounts of CK in transgenic potato plants. IPT expression promoted earlier sprouting in vitro. Strikingly, CKX-expressing tubers exhibited a prolonged dormancy period and did not respond to GA(3). This supports an essential role of CK in terminating tuber dormancy and indicates that GA is not sufficient to break dormancy in the absence of CK. GA(3)-treated wild-type and CKX-expressing tuber buds were subjected to a transcriptome analysis that revealed transcriptional changes in several functional groups, including cell wall metabolism, cell cycle, and auxin and ethylene signaling, denoting events associated with the reactivation of dormant meristems.

Down-regulation of gibberellic acid in poplar has negligible effects on host-plant suitability and insect pest response

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buhl, Christine; Strauss, Steven H.; Lindroth, Richard L.

Abstract Endogenous levels and signaling of gibberellin plant hormones such as gibberellic acid (GA) have been genetically down-regulated to create semi-dwarf varieties of poplar. The potential benefits of semi-dwarf stature include reduced risk of wind damage, improved stress tolerance, and improved wood quality. Despite these benefits, modification of growth traits may have consequences for non-target traits that confer defense against insect herbivores. According to the growth-differentiation balance hypothesis, reductions in growth may shift allocation of carbon from growth to chemical resistance traits, thereby altering plant defense. To date, host-plant suitability and pest response have not been comprehensively evaluated in GAmore » down-regulated plants. We quantified chemical resistance and nitrogen (an index of protein) in GA down-regulated and wild-type poplar (Populus alba × P. tremula) genotypes. We also evaluated performance of both generalist (Lymantria dispar) and specialist (Chrysomela scripta) insect pests reared on these genotypes. Our evaluation of resistance traits in four GA down-regulated genotypes revealed increased phenolic glycosides in one modified genotype and reduced lignin in two modified genotypes relative to the non-transgenic wild type. Nitrogen levels did not vary significantly among the experimental genotypes. Generalists reared on the four GA down-regulated genotypes exhibited reduced performance on only one modified genotype relative to the wild type. Specialists, however, performed similarly across all genotypes. Results from this study indicate that although some non-target traits varied among GA down-regulated genotypes, the differences in poplar pest susceptibility were modest and highly genotype-specific.« less

Down-regulation of gibberellic acid in poplar has negligible effects on host-plant suitability and insect pest response

DOE PAGES

Buhl, Christine; Strauss, Steven H.; Lindroth, Richard L.

2015-01-06

Abstract Endogenous levels and signaling of gibberellin plant hormones such as gibberellic acid (GA) have been genetically down-regulated to create semi-dwarf varieties of poplar. The potential benefits of semi-dwarf stature include reduced risk of wind damage, improved stress tolerance, and improved wood quality. Despite these benefits, modification of growth traits may have consequences for non-target traits that confer defense against insect herbivores. According to the growth-differentiation balance hypothesis, reductions in growth may shift allocation of carbon from growth to chemical resistance traits, thereby altering plant defense. To date, host-plant suitability and pest response have not been comprehensively evaluated in GAmore » down-regulated plants. We quantified chemical resistance and nitrogen (an index of protein) in GA down-regulated and wild-type poplar (Populus alba × P. tremula) genotypes. We also evaluated performance of both generalist (Lymantria dispar) and specialist (Chrysomela scripta) insect pests reared on these genotypes. Our evaluation of resistance traits in four GA down-regulated genotypes revealed increased phenolic glycosides in one modified genotype and reduced lignin in two modified genotypes relative to the non-transgenic wild type. Nitrogen levels did not vary significantly among the experimental genotypes. Generalists reared on the four GA down-regulated genotypes exhibited reduced performance on only one modified genotype relative to the wild type. Specialists, however, performed similarly across all genotypes. Results from this study indicate that although some non-target traits varied among GA down-regulated genotypes, the differences in poplar pest susceptibility were modest and highly genotype-specific.« less

The early inflorescence of Arabidopsis thaliana demonstrates positional effects in floral organ growth and meristem patterning.

PubMed

Plackett, Andrew R G; Powers, Stephen J; Phillips, Andy L; Wilson, Zoe A; Hedden, Peter; Thomas, Stephen G

2018-06-01

Linear modelling approaches detected significant gradients in organ growth and patterning across early flowers of the Arabidopsis inflorescence and uncovered evidence of new roles for gibberellin in floral development. Most flowering plants, including the genetic model Arabidopsis thaliana, produce multiple flowers in sequence from a reproductive shoot apex to form a flower spike (inflorescence). The development of individual flowers on an Arabidopsis inflorescence has typically been considered as highly stereotypical and uniform, but this assumption is contradicted by the existence of mutants with phenotypes visible in early flowers only. This phenomenon is demonstrated by mutants partially impaired in the biosynthesis of the phytohormone gibberellin (GA), in which floral organ growth is retarded in the first flowers to be produced but has recovered spontaneously by the 10th flower. We presently lack systematic data from multiple flowers across the Arabidopsis inflorescence to explain such changes. Using mutants of the GA 20-OXIDASE (GA20ox) GA biosynthesis gene family to manipulate endogenous GA levels, we investigated the dynamics of changing floral organ growth across the early Arabidopsis inflorescence (flowers 1-10). Modelling of floral organ lengths identified a significant, GA-independent gradient of increasing stamen length relative to the pistil in the wild-type inflorescence that was separable from other, GA-dependent effects. It was also found that the first flowers exhibited unstable organ patterning in contrast to later flowers and that this instability was prolonged by exogenous GA treatment. These findings indicate that the development of individual flowers is influenced by hitherto unknown factors acting across the inflorescence and also suggest novel functions for GA in floral patterning.

Physical basis for altered stem elongation rates in internode length mutants of Pisum

NASA Technical Reports Server (NTRS)

Behringer, F. J.; Cosgrove, D. J.; Reid, J. B.; Davies, P. J.

1990-01-01

Biophysical parameters related to gibberellin (GA)-dependent stem elongation were examined in dark-grown stem-length genotypes of Pisum sativum L. The rate of internode expansion in these genotypes is altered due to recessive mutations which affect either the endogenous levels of, or response to, GA. The GA deficient dwarf L181 (ls), two GA insensitive semierectoides dwarfs NGB5865 and NGB5862 (lka and lkb, respectively) and the slender' line L197 (la crys), which is tall regardless of GA content, were compared to the wild-type tall cultivar, Torsdag. Osmotic pressure, estimated by vapor pressure osmometry, and turgor pressure, measured directly with a pressure probe, did not correlate with the differences in growth rate among the genotypes. Mechanical wall properties of frozen-thawed tissue were measured using a constant force assay. GA deficiency resulted in increased wall stiffness judged both on the basis of plastic compliance and plastic extensibility normalized for equal stem circumference. Plastic compliance was not reduced in the GA insensitive dwarfs, though lka reduced circumference-normalized plasticity. In contrast, in vivo wall relaxation, determined by the pressure-block technique, differed among genotypes in a manner which did correlate with extension rates. The wall yield threshold was 1 bar or less in the tall lines, but ranged from 3 to 6 bars in the dwarf genotypes. The results with the ls mutant indicate that GA enhances stem elongation by both decreasing the wall yield threshold and increasing the wall yield coefficient. In the GA-insensitive mutants, lka and lkb, the wall yield threshold is substantially elevated. Plants possessing lka may also possess a reduced wall yield coefficient.

DELLA proteins negatively regulate dark-induced senescence and chlorophyll degradation in Arabidopsis through interaction with the transcription factor WRKY6.

PubMed

Zhang, Yongqiang; Liu, Zhongjuan; Wang, Xiaoyun; Wang, Jianfeng; Fan, Kai; Li, Zhaowei; Lin, Wenxiong

2018-03-24

DELLA proteins' negative regulation of dark-induced senescence and chlorophyll degradation in Arabidopsis is through interaction with WRKY6 and thus repression of its transcriptional activities on senescence-related genes. Senescence is an intricate and highly orchestrated process regulated by numerous endogenous and environmental signals. Gibberellins (GAs) and their signaling components DELLA proteins have been known to participate in the regulation of senescence. However, the mechanism of the GA-DELLA system involved in the senescence process remains largely unclear. Darkness is a known environmental factor that induces plant senescence. In this study, exogenous GA 3 (an active form of GA) accelerated but paclobutrazol (a specific GA biosynthesis inhibitor) retarded dark-induced leaf yellowing in Arabidopsis. Moreover, the dark-triggered decrease in chlorophyll content, increase in cell membrane leakage, and upregulation of senescence-associated genes were notably impaired in both endogenous GA-decreased mutants ga3ox1/ga3ox2 and ga20ox1/ga20ox2 compared with those in wild-type Col-0. These effects of darkness were enhanced in the quintuple mutant of DELLA genes gai-t6/rga-t2/rgl1-1/rgl2-1/rgl3-1 and conversely attenuated in the gain-of-function mutant gai and transgenic plant 35S::TAP-RGAd17 compared with wild-type Ler. Subsequently, RGA interacted with the transcription factor WRKY6 in a yeast two-hybrid assay, as confirmed by bimolecular fluorescence complementation and pull-down analyses. In addition, mutation and overexpression of WRKY6 retarded and accelerated dark-induced senescence, respectively. Furthermore, transient expression assays in Arabidopsis protoplasts indicated that RGA and GAI weakened the transcriptional activities of WRKY6 on its downstream senescence-related genes, including SAG13 and SGR. Taken together, these results suggest that GAs positively and DELLAs negatively regulate dark-induced senescence and chlorophyll degradation in Arabidopsis. DELLAs function in this process, at least in part, by interacting with WRKY6.

18β-Glycyrrhetinic acid protects against methotrexate-induced kidney injury by up-regulating the Nrf2/ARE/HO-1 pathway and endogenous antioxidants.

PubMed

Abd El-Twab, Sanaa M; Hozayen, Walaa G; Hussein, Omnia E; Mahmoud, Ayman M

2016-10-01

18β-glycyrrhetinic acid (18β-GA) has multiple beneficial and therapeutic effects. However, its protective roles on methotrexate (MTX)-induced renal injury are not well defined. In the present study, we investigated the possible protective effects of 18β-GA against MTX-induced nephrotoxicity in rats. 18β-GA (50 and 100 mg/kg) was administered for 7 days either before or after MTX. The rats were decapitated and kidney and serum samples were collected. MTX-induced renal injury in rats was evidenced by the significant (p < 0.001) increase in circulating kidney function markers and tumor necrosis factor alpha (TNF-α), as well as the histopathological alterations. MTX-induced rats exhibited significantly increased lipid peroxidation (p < 0.05) and nitric oxide (p < 0.001) levels, with concomitant marked (p < 0.001) decline in the antioxidant defenses. 18β-GA, administered either before or after MTX, produced a significant amelioration of circulating kidney function markers, TNF-α, kidney lipid peroxidation, nitric oxide, and antioxidant defenses. In addition, 18β-GA supplementation significantly up-regulated the mRNA abundance of both nuclear factor-erythroid 2-related factor 2 (Nrf2) and hemoxygenase 1 (HO-1) in the kidney of MTX-induced rats. These results indicate that 18β-GA has a protective effect on MTX-induced nephrotoxicity with possible mechanisms of attenuating oxidative stress and inflammation through up-regulating the Nrf2/ARE signaling. These findings make 18β-GA candidate as a potent agent in preventing MTX-induced kidney injury.

OsSUV3 transgenic rice maintains higher endogenous levels of plant hormones that mitigates adverse effects of salinity and sustains crop productivity.

PubMed

Sahoo, Ranjan Kumar; Ansari, Mohammad Wahid; Tuteja, Renu; Tuteja, Narendra

2014-01-01

The SUV3 (suppressor of Var 3) gene encodes a DNA and RNA helicase, which is localized in the mitochondria. Plant SUV3 has not yet been characterized in detail. However, the Arabidopsis ortholog of SUV3 (AT4G14790) has been shown to be involved in embryo sac development. Previously, we have reported that rice SUV3 functions as DNA and RNA helicase and provides salinity stress tolerance by maintaining photosynthesis and antioxidant machinery. Here, we report further analysis of the transgenic OsSUV3 rice plants under salt stress. The transgenic OsSUV3 overexpressing rice T1 lines showed significantly higher endogenous content of plant hormones viz., gibberellic acid (GA3), zeatin (Z) and indole-3-acetic acid (IAA) in leaf, stem and root as compared to wild-type (WT), vector control (VC) and antisense (AS) plants under salt (200 mM NaCl) stress condition. A similar trend of endogenous plant hormones profile was also reflected in the T2 generation of OsSUV3 transgenic rice under defined parameters and stress condition. In response to stress, OsSUV3 rice plants maintained plant hormone levels that regulate the expression of several stress-induced genes and reduce adverse effects of salt on plant growth and development and therefore sustains crop productivity.

Endogenous hormone levels and anatomical characters of haustoria in Santalum album L. seedlings before and after attachment to the host.

PubMed

Zhang, Xinhua; Teixeira da Silva, Jaime A; Duan, Jun; Deng, Rufang; Xu, Xinlan; Ma, Guohua

2012-06-15

The physiological and anatomical attributes of haustoria tissues in hemi-parasitic Santalum album L. seedlings, growing on the potential host, Kuhnia rosmarnifolia Vent., were investigated before and after attachment to the host. Quantization of endogenous levels of indole-3-acetic acid (IAA), zeatin (Z), zeatin riboside (ZR), GA-like substances (GAs) and abscisic acid (ABA) was performed by HPLC. Histological preparations were used to characterize structural differences between pre- and post-attachment haustoria. The contents of GAs and ABA were higher in attached haustoria, with 3.61 and 3.50μgg(-1) fresh weight, respectively, and three times higher than in non-attached haustoria. Cytokinins, Z, ZR and IAA levels were also high, and their contents in attached haustoria increased 2.04-, 2.17-, and 2.82-fold more, respectively, than in non-attached haustoria. A high auxin-to-cytokinin ratio contributed to haustorial development of S. album. A numerous amount of starch in parenchyma cells around the meristematic region above the haustorial gland and the endophyte tissue of the post-attachment haustoria were reported in a Santalaceae member for the first time. Many lysosomes were present and large-scale digestion of host cells occurred at the interface between the parasite and host. The haustorial penetration in S. album into the host stele was suggested to be a function of mechanical force and enzymatic activity. Analysis of the endogenous hormone levels and the structural characters in S. album haustoria indicated that the haustoria were able to synthesize phytohormones, which appeared to be necessary for cell division and differentiation during haustorial development. These results suggest that endogenous hormones are involved in the haustorial development of S. album and in water and nutrient transport in the host-parasite association. Copyright © 2012 Elsevier GmbH. All rights reserved.

Overexpression of GA20-OXIDASE1 impacts plant height, biomass allocation and saccharification efficiency in maize.

PubMed

Voorend, Wannes; Nelissen, Hilde; Vanholme, Ruben; De Vliegher, Alex; Van Breusegem, Frank; Boerjan, Wout; Roldán-Ruiz, Isabel; Muylle, Hilde; Inzé, Dirk

2016-03-01

Increased biomass yield and quality are of great importance for the improvement of feedstock for the biorefinery. For the production of bioethanol, both stem biomass yield and the conversion efficiency of the polysaccharides in the cell wall to fermentable sugars are of relevance. Increasing the endogenous levels of gibberellic acid (GA) by ectopic expression of GA20-OXIDASE1 (GA20-OX1), the rate-limiting step in GA biosynthesis, is known to affect cell division and cell expansion, resulting in larger plants and organs in several plant species. In this study, we examined biomass yield and quality traits of maize plants overexpressing GA20-OX1 (GA20-OX1). GA20-OX1 plants accumulated more vegetative biomass than control plants in greenhouse experiments, but not consistently over two years of field trials. The stems of these plants were longer but also more slender. Investigation of GA20-OX1 biomass quality using biochemical analyses showed the presence of more cellulose, lignin and cell wall residue. Cell wall analysis as well as expression analysis of lignin biosynthetic genes in developing stems revealed that cellulose and lignin were deposited earlier in development. Pretreatment of GA20-OX1 biomass with NaOH resulted in a higher saccharification efficiency per unit of dry weight, in agreement with the higher cellulose content. On the other hand, the cellulose-to-glucose conversion was slower upon HCl or hot-water pretreatment, presumably due to the higher lignin content. This study showed that biomass yield and quality traits can be interconnected, which is important for the development of future breeding strategies to improve lignocellulosic feedstock for bioethanol production. © 2015 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Phytohormones enabled endophytic fungal symbiosis improve aluminum phytoextraction in tolerant Solanum lycopersicum: An examples of Penicillium janthinellum LK5 and comparison with exogenous GA3.

PubMed

Khan, Abdul Latif; Waqas, Muhammad; Hussain, Javid; Al-Harrasi, Ahmed; Hamayun, Muhammad; Lee, In-Jung

2015-09-15

This work investigates the potentials of fungal-endophyte Penicillium janthinellum LK5 (PjLK5) and its inherent gibberellic acid (GA3) as reference to enhance aluminum (Al) induced toxicity in tolerant tomato (Solanum lycopersicum) plants. Initial screening showed significantly higher uptake of Al by PjLK5. Aluminum stress (100 μM) significantly retarted plant growth in control plants. Conversely PjLK5 and GA3 application significantly increased morphological attributes of Al-tolerant tomato plants with or without Al-stress. PjLK5 inoculation with and without Al-stress maintained the plant growth whilst extracting and translocating higher Al in shoot (∼ 1 92 mg/kg) and root (∼ 296 mg/kg). This was almost similar in GA3 treatments as well. In addition, PjLK5 inoculation extended protective effects to tomato plants by maintaining reduced cellular superoxide anions in Al stress. Al-induced oxidative stress was further reduced due to significantly higher activity of metal-responsive reduced glutathione. The functional membrane was less damaged in PjLK5 and GA3 treatments because the plants synthesized reduced levels of malondialdhyde, lenolenic and linoleic acids. Defense-related endogenous phytohormone salicylic acid was significantly up-regulated to counteract the adverse effects of Al-stress. In conclusion, the PjLK5 possess a similar bio-prospective potential as of GA3. Application of such biochemically active endophyte could increase metal phytoextraction whilst maintaining crop physiological homeostasis. Copyright © 2015 Elsevier B.V. All rights reserved.

Natural Variation of Molecular and Morphological Gibberellin Responses.

PubMed

Nam, Youn-Jeong; Herman, Dorota; Blomme, Jonas; Chae, Eunyoung; Kojima, Mikiko; Coppens, Frederik; Storme, Veronique; Van Daele, Twiggy; Dhondt, Stijn; Sakakibara, Hitoshi; Weigel, Detlef; Inzé, Dirk; Gonzalez, Nathalie

2017-01-01

Although phytohormones such as gibberellins are essential for many conserved aspects of plant physiology and development, plants vary greatly in their responses to these regulatory compounds. Here, we use genetic perturbation of endogenous gibberellin levels to probe the extent of intraspecific variation in gibberellin responses in natural accessions of Arabidopsis (Arabidopsis thaliana). We find that these accessions vary greatly in their ability to buffer the effects of overexpression of GA20ox1, encoding a rate-limiting enzyme for gibberellin biosynthesis, with substantial differences in bioactive gibberellin concentrations as well as transcriptomes and growth trajectories. These findings demonstrate a surprising level of flexibility in the wiring of regulatory networks underlying hormone metabolism and signaling. © 2017 American Society of Plant Biologists. All Rights Reserved.

Rice HOX12 Regulates Panicle Exsertion by Directly Modulating the Expression of ELONGATED UPPERMOST INTERNODE1[OPEN

PubMed Central

Gao, Shaopei; Fang, Jun; Xu, Fan; Wang, Wei

2016-01-01

Bioactive gibberellins (GAs) are key endogenous regulators of plant growth. Previous work identified ELONGATED UPPERMOST INTERNODE1 (EUI1) as a GA-deactivating enzyme that plays an important role in panicle exsertion from the flag leaf sheath in rice (Oryza sativa). However, the mechanism that regulates EUI1 activity during development is still largely unexplored. In this study, we identified the dominant panicle enclosure mutant regulator of eui1 (ree1-D), whose phenotype is caused by the activation of the homeodomain-leucine zipper transcription factor HOX12. Diminished HOX12 expression by RNA interference enhanced panicle exsertion, mimicking the eui1 phenotype. HOX12 knockdown plants contain higher levels of the major biologically active GAs (such as GA1 and GA4) than the wild type. The expression of EUI1 is elevated in the ree1-D mutant but reduced in HOX12 knockdown plants. Interestingly, both HOX12 and EUI1 are predominantly expressed in panicles, where GA4 is highly accumulated. Yeast one-hybrid, electrophoretic mobility shift assay, and chromatin immunoprecipitation analyses showed that HOX12 physically interacts with the EUI1 promoter both in vitro and in vivo. Furthermore, plants overexpressing HOX12 in the eui1 mutant background retained the elongated uppermost internode phenotype. These results indicate that HOX12 acts directly through EUI1 to regulate panicle exsertion in rice. PMID:26977084

GID1 modulates stomatal response and submergence tolerance involving abscisic acid and gibberellic acid signaling in rice.

PubMed

Du, Hao; Chang, Yu; Huang, Fei; Xiong, Lizhong

2015-11-01

Plant responses to abiotic stresses are coordinated by arrays of growth and developmental programs. Gibberellic acid (GA) and abscisic acid (ABA) play critical roles in the developmental programs and environmental responses, respectively, through complex signaling and metabolism networks. However, crosstalk between the two phytohormones in stress responses remains largely unknown. In this study, we report that GIBBERELLIN-INSENSITIVE DWARF 1 (GID1), a soluble receptor for GA, regulates stomatal development and patterning in rice (Oryza sativa L.). The gid1 mutant showed impaired biosynthesis of endogenous ABA under drought stress conditions, but it exhibited enhanced sensitivity to exogenous ABA. Scanning electron microscope and infrared thermal image analysis indicated an increase in the stomatal conductance in the gid1 mutant under drought conditions. Interestingly, the gid1 mutant had increased levels of chlorophyll and carbohydrates under submergence conditions, and showed enhanced reactive oxygen species (ROS)-scavenging ability and submergence tolerance compared with the wild-type. Further analyses suggested that the function of GID1 in submergence responses is partially dependent on ABA, and GA signaling by GID1 is involved in submergence tolerance by modulating carbohydrate consumption. Taken together, these findings suggest GID1 plays distinct roles in stomatal response and submergence tolerance through both the ABA and GA signaling pathways in rice. © 2014 Institute of Botany, Chinese Academy of Sciences.

Hydrolysis and reconjugation of gibberellin A20 glucosyl ester by seedlings of Zea mays L.

PubMed Central

Schneider, G; Jensen, E; Spray, C R; Phinney, B O

1992-01-01

The [6-2H]glucosyl ester of [17-13C,3H]gibberellin A20 (GA20) was injected into light-grown 14-day-old seedlings of normal, dwarf-1, and dwarf-5 maize (Zea mays L.). The plant material was extracted 24 h later, and the extracts were purified by solvent partitioning, column chromatography, and HPLC. 13C-labeled metabolites were identified from the purified extracts by full-scan gas chromatography/mass spectrometry and selected ion current monitoring in conjunction with Kovats retention indices. The metabolites, [13C]GA20, [13C]GA29, [13C]GA20-13-O-glucoside, and [13C]GA29-2-O-glucoside, were identified from normal, dwarf-1, and dwarf-5 seedlings. [13C]GA8 and [13C]GA8-2-O-glucoside were also identified from normal and dwarf-5 seedlings but not from dwarf-1 seedlings. The data provide definitive evidence for the endogenous hydrolysis by the seedlings of the introduced conjugate and its reconjugation to three glucosides. PMID:1518829

Exogenous abscisic acid alleviates zinc uptake and accumulation in Populus × canescens exposed to excess zinc.

PubMed

Shi, Wen-Guang; Li, Hong; Liu, Tong-Xian; Polle, Andrea; Peng, Chang-Hui; Luo, Zhi-Bin

2015-01-01

A greenhouse experiment was conducted to study whether exogenous abscisic acid (ABA) mediates the responses of poplars to excess zinc (Zn). Populus × canescens seedlings were treated with either basal or excess Zn levels and either 0 or 10 μm ABA. Excess Zn led to reduced photosynthetic rates, increased Zn accumulation, induced foliar ABA and salicylic acid (SA), decreased foliar gibberellin (GA3 ) and auxin (IAA), elevated root H2 O2 levels, and increased root ratios of glutathione (GSH) to GSSG and foliar ratios of ascorbate (ASC) to dehydroascorbate (DHA) in poplars. While exogenous ABA decreased foliar Zn concentrations with 7 d treatments, it increased levels of endogenous ABA, GA3 and SA in roots, and resulted in highly increased foliar ASC accumulation and ratios of ASC to DHA. The transcript levels of several genes involved in Zn uptake and detoxification, such as yellow stripe-like family protein 2 (YSL2) and plant cadmium resistance protein 2 (PCR2), were enhanced in poplar roots by excess Zn but repressed by exogenous ABA application. These results suggest that exogenous ABA can decrease Zn concentrations in P. × canescens under excess Zn for 7 d, likely by modulating the transcript levels of key genes involved in Zn uptake and detoxification. © 2014 John Wiley & Sons Ltd.

Development of Agrobacterium-Mediated Virus-Induced Gene Silencing and Performance Evaluation of Four Marker Genes in Gossypium barbadense

PubMed Central

Pang, Jinhuan; Zhu, Yue; Li, Qing; Liu, Jinzhi; Tian, Yingchuan; Liu, Yule; Wu, Jiahe

2013-01-01

Gossypium barbadense is a cultivated cotton species and possesses many desirable traits, including high fiber quality and resistance to pathogens, especially Verticilliumdahliae (a devastating pathogen of Gossypium hirsutum, the main cultivated species). These elite traits are difficult to be introduced into G. hirsutum through classical breeding methods. In addition, genetic transformation of G . barbadense has not been successfully performed. It is therefore important to develop methods for evaluating the function and molecular mechanism of genes in G . barbadense . In this study, we had successfully introduced a virus-induced gene silencing (VIGS) system into three cultivars of G . barbadense by inserting marker genes into the tobacco rattle virus (TRV) vector. After we optimized the VIGS conditions, including light intensity, photoperiod, seedling age and Agrobacterium strain, 100% of plants agroinfiltrated with the GaPDS silencing vector showed white colored leaves. Three other marker genes, GaCLA1, GaANS and GaANR, were employed to further test this VIGS system in G . barbadense . The transcript levels of the endogenous genes in the silenced plants were reduced by more than 99% compared to control plants; these plants presented phenotypic symptoms 2 weeks after inoculation. We introduced a fusing sequence fragment of GaPDS and GaANR gene silencing vectors into a single plant, which resulted in both photobleaching and brownish coloration. The extent of silencing in plants agroinfiltrated with fusing two-gene-silencing vector was consistent with plants harboring a single gene silencing vector. The development of this VIGS system should promote analysis of gene function in G . barbadense , and help to contribute desirable traits for breeding of G . barbadense and G. hirsutum. PMID:24023833

Human milk peptides differentiate between the preterm and term infant and across varying lactational stages.

PubMed

Dingess, Kelly A; de Waard, Marita; Boeren, Sjef; Vervoort, Jacques; Lambers, Tim T; van Goudoever, Johannes B; Hettinga, Kasper

2017-10-18

Variations in endogenous peptide profiles, functionality, and the enzymes responsible for the formation of these peptides in human milk are understudied. Additionally, there is a lack of knowledge regarding peptides in donor human milk, which is used to feed preterm infants when mother's own milk is not (sufficiently) available. To assess this, 29 human milk samples from the Dutch Human Milk Bank were analyzed as three groups, preterm late lactation stage (LS) (n = 12), term early (n = 8) and term late LS (n = 9). Gestational age (GA) groups were defined as preterm (24-36 weeks) and term (≥37 weeks). LS was determined as days postpartum as early (16-36 days) or late (55-88 days). Peptides, analyzed by LC-MS/MS, and parent proteins (proteins from matched peptide sequences) were identified and quantified, after which peptide functionality and the enzymes responsible for protein cleavage were determined. A total of 16 different parent proteins were identified from human milk, with no differences by GA or LS. We identified 1104 endogenous peptides, of which, the majority were from the parent proteins β-casein, polymeric immunoglobulin receptor, α s1 -casein, osteopontin, and κ-casein. The absolute number of peptides differed by GA and LS with 30 and 41 differing sequences respectively (p < 0.05) Odds likelihood tests determined that 32 peptides had a predicted bioactive functionality, with no significant differences between groups. Enzyme prediction analysis showed that plasmin/trypsin enzymes most likely cleaved the identified human milk peptides. These results explain some of the variation in endogenous peptides in human milk, leading to future targets that may be studied for functionality.

The rice GERMINATION DEFECTIVE 1, encoding a B3 domain transcriptional repressor, regulates seed germination and seedling development by integrating GA and carbohydrate metabolism

PubMed Central

Guo, Xiaoli; Hou, Xiaomei; Fang, Jun; Wei, Piwei; Xu, Bo; Chen, Mingluan; Feng, Yuqi; Chu, Chengcai

2013-01-01

It has been shown that seed development is regulated by a network of transcription factors in Arabidopsis including LEC1 (LEAFY COTYLEDON1), L1L (LEC1-like) and the B3 domain factors LEC2, FUS3 (FUSCA3) and ABI3 (ABA-INSENSITIVE3); however, molecular and genetic regulation of seed development in cereals is poorly understood. To understand seed development and seed germination in cereals, a large-scale screen was performed using our T–DNA mutant population, and a mutant germination-defective1 (gd1) was identified. In addition to the severe germination defect, the gd1 mutant also shows a dwarf phenotype and abnormal flower development. Molecular and biochemical analyses revealed that GD1 encodes a B3 domain-containing transcription factor with repression activity. Consistent with the dwarf phenotype of gd1, expression of the gibberelic acid (GA) inactivation gene OsGA2ox3 is increased dramatically, accompanied by reduced expression of GA biosynthetic genes including OsGA20ox1, OsGA20ox2 and OsGA3ox2 in gd1, resulting in a decreased endogenous GA4 level. Exogenous application of GA not only induced GD1 expression, but also partially rescued the dwarf phenotype of gd1. Furthermore, GD1 binds to the promoter of OsLFL1, a LEC2/FUS3-like gene of rice, via an RY element, leading to significant up-regulation of OsLFL1 and a large subset of seed maturation genes in the gd1 mutant. Plants over-expressing OsLFL1 partly mimic the gd1 mutant. In addition, expression of GD1 was induced under sugar treatment, and the contents of starch and soluble sugar are altered in the gd1 mutant. These data indicate that GD1 participates directly or indirectly in regulating GA and carbohydrate homeostasis, and further regulates rice seed germination and seedling development. PMID:23581288

Auxin-to-Gibberellin Ratio as a Signal for Light Intensity and Quality in Regulating Soybean Growth and Matter Partitioning

PubMed Central

Yang, Feng; Fan, Yuanfang; Wu, Xiaoling; Cheng, Yajiao; Liu, Qinlin; Feng, Lingyang; Chen, Junxu; Wang, Zhonglin; Wang, Xiaochun; Yong, Taiwen; Liu, Weiguo; Liu, Jiang; Du, Junbo; Shu, Kai; Yang, Wenyu

2018-01-01

The intensity and quality (red to far-red (R/Fr) ratio) of light directly affect growth of plant under shading. Gibberellins (GAs) and auxin [indole-3-acetic acid (IAA)] play important roles in mediating the shading adaptive responses of plants. Thus, the intensity and quality of the uncoupling light from shading were assessed to identify the influence of each component on the morphology and matter distribution of the leaf, stem, and petiole. This assessment was based on the changes in endogenous Gibberellin 1 (GA1) and IAA levels. Soybean plants were grown in a growth chamber with four treatments [normal (N), N+Fr, low (L), and L+Fr light]. Results revealed that the reductions in photosynthetically active radiation (PAR) and R/Fr ratio equally increased height and stem mass fractions (SMFs) of the soybean seedling. The light intensity significantly influenced the dry mass per unit area and mass fraction of soybean leaves, whereas the light quality regulated the petiole elongation and mass fraction. Low R/Fr ratio (high Fr light) increased the soybean biomass by improving the photosynthetic assimilation rate and quantum yield of photosystem II. In addition, the IAA and GA1 levels in the leaf, stem, and petiole did not reflect the growth response trends of each tissue toward light intensity and quality; however, trends of the IAA-to-GA1 content ratios were similar to those of the growth and matter allocation of each soybean tissue under different light environments. Therefore, the response of growth and matter allocation of soybean to light intensity and quality may be regulated by the IAA-to-GA1 content ratio in the tissues of the soybean plant. PMID:29441084

Formation of the Archean crust of the ancient Vodlozero domain (Baltic shield)

NASA Astrophysics Data System (ADS)

Arestova, N. A.; Chekulaev, V. P.; Lobach-Zhuchenko, S. B.; Kucherovskii, G. A.

2015-03-01

The available geological, petrological, and isotopic data on Archean rocks of the Baltic shield are used to analyze the formation of the crust of the ancient Vodlozero domain. This made it possible to reveal the succession of endogenic processes in different parts of the domain and correlate them between each other. Several stages of magmatic processes reflecting changes in magma-generation environments are definable in the crust formation. The earliest stages of magmatism (3.24 and 3.13-3.15 Ga) are mostly represented by rocks of the tonalite-trondhjemite-granodiorite association. The next stage of endogenic activity (3020-2900 Ma) was marked by the formation of volcanics of the komatiite-basalt and andesite-dacite associations constituting greenstone belts in marginal parts of the Vodlozero domain and basic dikes accompanied by layered pyroxenite-norite-diorite intrusion in its central part. These basic bodies crossing earlier tonalities were formed in extension settings related to the formation of the mantle plume, which is confirmed by the rock composition. This stage culminated in the formation of trondhjemites at margins of greenstone structure. The next stage of endogenic activity commenced at 2890-2840 Ma by the emplacement of high-magnesian gabbro and diorite dikes in the western margin of the domain, where they cross rocks of the tonalitetrondhjemite association. This stage was marked by the formation of intermediate-acid subvolcanic bodies and dikes as well as basite intrusions including the layered and differentiated Semch intrusion, the largest one in the Vodlozero domain. The stage culminated at approximately 2850 Ma in the emplacement of tonalities of the limited distribution being represented by the Shilos massif in the north of the domain and Shal'skii massif on the eastern shore of Lake Onega. The important stage in the geological history of the Vodlozero domain is the formation of the intracratonic Matkalakhta greenstone belt at approximately 2.8 Ga, which includes arenite quartzite and graywackes and polymictic conglomerates developed in the Lake Oster area in addition to volcanics. These rocks indicate a stable tectonic regime, which resulted in deep erosion of the crust. The emplacement of sanukitoids (2.73-2.74 Ga) as well as subsequent two-feldspar granites (2.68-2.70 Ga) and basite dikes (2.61-2.65 Ga) may be considered as resulting from the plume influence on the relatively stabilized sialic crust of the Baltic shield.

Gibberellins Producing Endophytic Fungus Porostereum spadiceum AGH786 Rescues Growth of Salt Affected Soybean

PubMed Central

Hamayun, Muhammad; Hussain, Anwar; Khan, Sumera A.; Kim, Ho-Youn; Khan, Abdul L.; Waqas, Muhammad; Irshad, Muhammad; Iqbal, Amjad; Rehman, Gauhar; Jan, Samin; Lee, In-Jung

2017-01-01

In the pursuit of sustainable agriculture through environment and human health friendly practices, we evaluated the potential of a novel gibberellins (GAs) producing basidiomycetous endophytic fungus Porostereum spadiceum AGH786, for alleviating salt stress and promoting health benefits of soybean. Soybean seedlings exposed to different levels of NaCl stress (70 and 140 mM) under greenhouse conditions, were inoculated with the AGH786 strain. Levels of phytohormones including GAs, JA and ABA, and isoflavones were compared in control and the inoculated seedlings to understand the mechanism through which the stress is alleviated. Gibberellins producing endophytic fungi have been vital for promoting plant growth under normal and stress conditions. We report P. spadiceum AGH786 as the ever first GAs producing basidiomycetous fungus capable of producing six types of GAs. In comparison to the so for most efficient GAs producing Gibberella fujikuroi, AGH786 produced significantly higher amount of the bioactive GA3. Salt-stressed phenotype of soybean seedlings was characterized by low content of GAs and high amount of ABA and JA with reduced shoot length, biomass, leaf area, chlorophyll contents, and rate of photosynthesis. Mitigation of salt stress by AGH786 was always accompanied by high GAs, and low ABA and JA, suggesting that this endophytic fungus reduces the effect of salinity by modulating endogenous phytohormones of the seedlings. Additionally, this strain also enhanced the endogenous level of two isoflavones including daidzen and genistein in soybean seedlings under normal as well as salt stress conditions as compared to their respective controls. P. spadiceum AGH786 boosted the NaCl stress tolerance and growth in soybean, by modulating seedlings endogenous phytohormones and isoflavones suggesting a valuable contribution of this potent fungal biofertilizer in sustainable agriculture in salt affected soils. PMID:28473818

Reactive oxygen species induced by heat stress during grain filling of rice (Oryza sativa L.) are involved in occurrence of grain chalkiness.

PubMed

Suriyasak, Chetphilin; Harano, Keisuke; Tanamachi, Koichiro; Matsuo, Kazuhiro; Tamada, Aina; Iwaya-Inoue, Mari; Ishibashi, Yushi

2017-09-01

Heat stress during grain filling increases rice grain chalkiness due to increased activity of α-amylase, which hydrolyzes starch. In rice and barley seeds, reactive oxygen species (ROS) produced after imbibition induce α-amylase activity via regulation of gibberellin (GA) and abscisic acid (ABA) levels during seed germination. Here, we examined whether ROS is involved in induction of grain chalkiness by α-amylase in developing rice grains under heat stress. To elucidate the role of ROS in grain chalkiness, we grew post-anthesis rice plants (Oryza sativa L. cv. Koshihikari) under control (25°C) or heat stress (30°C) conditions with or without antioxidant (dithiothreitol) treatment. The developing grains were analyzed for expression of NADPH oxidases, GA biosynthesis genes (OsGA3ox1, OsGA20ox1), ABA catabolism genes (OsABA8'OH1, OsABA8'OH2) and an α-amylase gene (OsAmy3E), endogenous H 2 O 2 content and the grain quality. In grains exposed to heat stress, the expression of NADPH oxidase genes (especially, OsRbohB, OsRbohD, OsRbohF and OsRbohI) and the ROS content increased. Heat stress also increased the expression of OsGA3ox1, OsGA20ox1, OsABA8'OH1, OsABA8'OH2 and OsAmy3E. On the other hand, dithiothreitol treatment reduced the effects of heat stress on the expression of these genes and significantly reduced grain chalkiness induced by heat stress. These results suggest that, similar to cereal seed germination mechanism, ROS produced under heat stress is involved in α-amylase induction in maturating rice grains through GA/ABA metabolism, and consequently caused grain chalkiness. Copyright © 2017 Elsevier GmbH. All rights reserved.

Leaf-induced gibberellin signaling is essential for internode elongation, cambial activity, and fiber differentiation in tobacco stems.

PubMed

Dayan, Jonathan; Voronin, Nickolay; Gong, Fan; Sun, Tai-ping; Hedden, Peter; Fromm, Hillel; Aloni, Roni

2012-01-01

The gibberellins (GAs) are a group of endogenous compounds that promote the growth of most plant organs, including stem internodes. We show that in tobacco (Nicotiana tabacum) the presence of leaves is essential for the accumulation of bioactive GAs and their immediate precursors in the stem and consequently for normal stem elongation, cambial proliferation, and xylem fiber differentiation. These processes do not occur in the absence of maturing leaves but can be restored by application of C(19)-GAs, identifying the presence of leaves as a requirement for GA signaling in stems and revealing the fundamental role of GAs in secondary growth regulation. The use of reporter genes for GA activity and GA-directed DELLA protein degradation in Arabidopsis thaliana confirms the presence of a mobile signal from leaves to the stem that induces GA signaling.

Leaf-Induced Gibberellin Signaling Is Essential for Internode Elongation, Cambial Activity, and Fiber Differentiation in Tobacco Stems[C][W

PubMed Central

Dayan, Jonathan; Voronin, Nickolay; Gong, Fan; Sun, Tai-ping; Hedden, Peter; Fromm, Hillel; Aloni, Roni

2012-01-01

The gibberellins (GAs) are a group of endogenous compounds that promote the growth of most plant organs, including stem internodes. We show that in tobacco (Nicotiana tabacum) the presence of leaves is essential for the accumulation of bioactive GAs and their immediate precursors in the stem and consequently for normal stem elongation, cambial proliferation, and xylem fiber differentiation. These processes do not occur in the absence of maturing leaves but can be restored by application of C19-GAs, identifying the presence of leaves as a requirement for GA signaling in stems and revealing the fundamental role of GAs in secondary growth regulation. The use of reporter genes for GA activity and GA-directed DELLA protein degradation in Arabidopsis thaliana confirms the presence of a mobile signal from leaves to the stem that induces GA signaling. PMID:22253226

Gibberellin-producing Promicromonospora sp. SE188 improves Solanum lycopersicum plant growth and influences endogenous plant hormones.

PubMed

Kang, Sang-Mo; Khan, Abdul Latif; Hamayun, Muhammad; Hussain, Javid; Joo, Gil-Jae; You, Young-Hyun; Kim, Jong-Guk; Lee, In-Jung

2012-12-01

Plant growth-promoting rhizobacteria (PGPR) producing gibberellins (GAs) can be beneficial to plant growth and development. In the present study, we isolated and screened a new strain of Promicromonospora sp., SE188, isolated from soil. Promicromonospora sp. SE188 secreted GAs into its growth medium and exhibited phosphate solubilization potential. The PGPR produced physiologically active (GA(1) and GA(4)) and inactive (GA(9), GA(12), GA(19), GA(20), GA(24), GA(34), and GA(53)) GAs in various quantities detected by GC/MS-SIM. Solanum lycopersicum (tomato) plants inoculated with Promicromonospora sp. SE188 showed a significantly higher shoot length and biomass as compared to controls where PGPR-free nutrient broth (NB) and distilled water (DW) were applied to plants. The presence of Promicromonospora sp. SE188 significantly up-regulated the non C-13 hydroxylation GA biosynthesis pathway (GA(12)→GA(24)→GA(9)→GA(4)→ GA(34)) in the tomato plants as compared to the NB and DW control plants. Abscisic acid, a plant stress hormone, was significantly down-regulated in the presence of Promicromonospora sp. SE188. Contrarily, salicylic acid was significantly higher in the tomato plant after Promicromonospora sp. SE188 inoculation as compared to the controls. Promicromonospora sp. SE188 showed promising stimulation of tomato plant growth. From the results it appears that Promicromonospora sp. SE188 has potential as a bio-fertilizer and should be more broadly tested in field trials for higher crop production in eco-friendly farming systems.

Exogenous short-term silicon application regulates macro-nutrients, endogenous phytohormones, and protein expression in Oryza sativa L.

PubMed

Jang, Soo-Won; Kim, Yoonha; Khan, Abdul Latif; Na, Chae-In; Lee, In-Jung

2018-01-04

Silicon (Si) has been known to regulate plant growth; however, the underlying mechanisms of short-term exogenous Si application on the regulation of calcium (Ca) and nitrogen (N), endogenous phytohormones, and expression of essential proteins have been little understood. Exogenous Si application significantly increased Si content as compared to the control. Among Si treatments, 1.0 mM Si application showed increased phosphorus content as compared to other Si treatments (0.5, 2.0, and 4.0 mM). However, Ca accumulation was significantly reduced (1.8- to 2.0-fold) at the third-leaf stage in the control, whereas all Si treatments exhibited a dose-dependent increase in Ca as determined by radioisotope 45 Ca analysis. Similarly, the radioisotope 15 N for nitrogen localization and uptake showed a varying but reduced response (ranging from 1.03-10.8%) to different Si concentrations as compared to 15 N application alone. Physiologically active endogenous gibberellin (GA 1 ) was also significantly higher with exogenous Si (1.0 mM) as compared to GA 20 and the control plants. A similar response was noted for endogenous jasmonic and salicylic acid synthesis in rice plants with Si application. Proteomic analysis revealed the activation of several essential proteins, such as Fe-S precursor protein, putative thioredoxin, Ser/Thr phosphatase, glucose-6-phosphate isomerase (G6P), and importin alpha-1b (Imp3), with Si application. Among the most-expressed proteins, confirmatory gene expression analysis for G6P and Imp3 showed a similar response to those of the Si treatments. In conclusion, the current results suggest that short-term exogenous Si can significantly regulate rice plant physiology by influencing Ca, N, endogenous phytohormones, and proteins, and that 1.0 mM Si application is more beneficial to plants than higher concentrations.

Ethylene-mediated regulation of gibberellin content and growth in helianthus annuus L

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pearce, D.W.; Reid, D.M.; Pharis, R.P.

1991-04-01

Elongation of hypocotyls of sunflower can be promoted by gibberellins (GAs) and inhibited by ethylene. The role of these hormones in regulating elongation was investigated by measuring changes in both endogenous GAs and in the metabolism of exogenous ({sup 3}H)- and ({sup 2}H{sub 2})GA{sub 20} in the hypocotyls of sunflower (Helianthus annuus L. cv Delgren 131) seedlings exposed to ethylene. The major biologically active GAs identified by gas chromatography-mass spectrometry were GA{sub 1}, GA{sub 19}, GA{sub 20}, and GA{sub 44}. In hypocotyls of seedlings exposed to ethylene, the concentration of GA{sub 1}, known to be directly active in regulating shootmore » elongation in a number of species, was reduced. Ethylene treatment reduced the metabolism of ({sup 3}H)GA{sub 20} and less ({sup 2}H{sub 2})GA{sub 1} was found in the hypocotyls of those seedlings exposed to the higher ethylene concentrations. However, it is not known if the effect of ethylene on GA{sub 20} metabolism was direct or indirect. In seedlings treated with exogenous GA{sub 1} or GA{sub 3}, the hypocotyls elongated faster than those of controls, but the GA treatment only partially overcame the inhibitory effect of ethylene on elongation. The authors conclude that GA content is a factor which may limit elongation in hypocotyls of sunflower, and that while exposure to ethylene results in reduced concentration of GA{sub 1} this is not sufficient per se to account for the inhibition of elongation caused by ethylene.« less

Transcriptome Analysis Reveals that Red and Blue Light Regulate Growth and Phytohormone Metabolism in Norway Spruce [Picea abies (L.) Karst].

PubMed

OuYang, Fangqun; Mao, Jian-Feng; Wang, Junhui; Zhang, Shougong; Li, Yue

2015-01-01

The mechanisms by which different light spectra regulate plant shoot elongation vary, and phytohormones respond differently to such spectrum-associated regulatory effects. Light supplementation can effectively control seedling growth in Norway spruce. However, knowledge of the effective spectrum for promoting growth and phytohormone metabolism in this species is lacking. In this study, 3-year-old Norway spruce clones were illuminated for 12 h after sunset under blue or red light-emitting diode (LED) light for 90 d, and stem increments and other growth traits were determined. Endogenous hormone levels and transcriptome differences in the current needles were assessed to identify genes related to the red and blue light regulatory responses. The results showed that the stem increment and gibberellin (GA) levels of the seedlings illuminated by red light were 8.6% and 29.0% higher, respectively, than those of the seedlings illuminated by blue light. The indoleacetic acid (IAA) level of the seedlings illuminated by red light was 54.6% lower than that of the seedlings illuminated by blue light, and there were no significant differences in abscisic acid (ABA) or zeatin riboside [ZR] between the two groups of seedlings. The transcriptome results revealed 58,736,166 and 60,555,192 clean reads for the blue-light- and red-light-illuminated samples, respectively. Illumina sequencing revealed 21,923 unigenes, and 2744 (approximately 93.8%) out of 2926 differentially expressed genes (DEGs) were found to be upregulated under blue light. The main KEGG classifications of the DEGs were metabolic pathway (29%), biosynthesis of secondary metabolites (20.49%) and hormone signal transduction (8.39%). With regard to hormone signal transduction, AUXIN-RESISTANT1 (AUX1), AUX/IAA genes, auxin-inducible genes, and early auxin-responsive genes [(auxin response factor (ARF) and small auxin-up RNA (SAUR)] were all upregulated under blue light compared with red light, which might have yielded the higher IAA level. DELLA and phytochrome-interacting factor 3 (PIF3), involved in negative GA signaling, were also upregulated under blue light, which may be related to the lower GA level. Light quality also affects endogenous hormones by influencing secondary metabolism. Blue light promoted phenylpropanoid biosynthesis, phenylalanine metabolism, flavonoid biosynthesis and flavone and flavonol biosynthesis, accompanied by upregulation of most of the genes in their pathways. In conclusion, red light may promote stem growth by regulating biosynthesis of GAs, and blue light may promote flavonoid, lignin, phenylpropanoid and some hormones (such as jasmonic acid) which were related to plant defense in Norway spruce, which might reduce the primary metabolites available for plant growth.

Effect of CPPU on Carbohydrate and Endogenous Hormone Levels in Young Macadamia Fruit

PubMed Central

Lu, Chaozhong; Lin, Wenqiu; Zou, Minghong; Zhang, Hanzhou; Wan, Jifeng; Huang, Xuming

2016-01-01

N-(2-Chloro-4-pyridyl)-N′-phenylurea (CPPU) is a highly active cytokinin-like plant growth regulator that promotes chlorophyll biosynthesis, cell division, and cell expansion. It also increases fruit set and accelerates fruit enlargement. However, there has been no report about the effect of CPPU on fruit development and its physiological mechanism in macadamia. In this study, we investigated the effect of CPPU treatment at early fruit development via foliar spray or raceme soaking at 20 mg·L-1 on fruit set and related physiology in macadamia. Changes in carbohydrate contents and endogenous hormones in leaves, bearing shoots and fruit were also examined. Results showed that CPPU significantly reduced young fruit drop and delayed the wave of fruit drop by 1–2 weeks. The treatment significantly decreased the contents of total soluble sugars and starch in the leaves, but increased them in the bearing shoots and total soluble sugars in the husk (pericarp) and seeds. These findings suggested that CPPU promoted carbohydrate mobilization from the leaves to the fruit. In addition, CPPU increased the contents of indole-3-acetic acid (IAA), gibberellin acid (GA3), and zeatin riboside (ZR) and decreased the abscisic acid (ABA) in the husk. Therefore, CPPU treatment reduced the early fruit drop by increasing carbohydrate availability and by modifying the balance among endogenous hormones. PMID:27387814

Post-Stroke Depression Modulation and in Vivo Antioxidant Activity of Gallic Acid and Its Synthetic Derivatives in a Murine Model System.

PubMed

Nabavi, Seyed Fazel; Habtemariam, Solomon; Di Lorenzo, Arianna; Sureda, Antoni; Khanjani, Sedigheh; Nabavi, Seyed Mohammad; Daglia, Maria

2016-04-28

Gallic acid (3,4,5-trihydroxybenzoic acid, GA) is a plant secondary metabolite, which shows antioxidant activity and is commonly found in many plant-based foods and beverages. Recent evidence suggests that oxidative stress contributes to the development of many human chronic diseases, including cardiovascular and neurodegenerative pathologies, metabolic syndrome, type 2 diabetes and cancer. GA and its derivative, methyl-3-O-methyl gallate (M3OMG), possess physiological and pharmacological activities closely related to their antioxidant properties. This paper describes the antidepressive-like effects of intraperitoneal administration of GA and two synthetic analogues, M3OMG and P3OMG (propyl-3-O-methylgallate), in balb/c mice with post-stroke depression, a secondary form of depression that could be due to oxidative stress occurring during cerebral ischemia and the following reperfusion. Moreover, this study determined the in vivo antioxidant activity of these compounds through the evaluation of superoxide dismutase (SOD) and catalase (Cat) activity, thiobarbituric acid-reactive substances (TBARS) and reduced glutathione (GSH) levels in mouse brain. GA and its synthetic analogues were found to be active (at doses of 25 and 50 mg/kg) in the modulation of depressive symptoms and the reduction of oxidative stress, restoring normal behavior and, at least in part, antioxidant endogenous defenses, with M3OMG being the most active of these compounds. SOD, TBARS, and GSH all showed strong correlation with behavioral parameters, suggesting that oxidative stress is tightly linked to the pathological processes involved in stroke and PSD. As a whole, the obtained results show that the administration of GA, M3OMG and P3OMG induce a reduction in depressive symptoms and oxidative stress.

Post-Stroke Depression Modulation and in Vivo Antioxidant Activity of Gallic Acid and Its Synthetic Derivatives in a Murine Model System

PubMed Central

Nabavi, Seyed Fazel; Habtemariam, Solomon; Di Lorenzo, Arianna; Sureda, Antoni; Khanjani, Sedigheh; Nabavi, Seyed Mohammad; Daglia, Maria

2016-01-01

Gallic acid (3,4,5-trihydroxybenzoic acid, GA) is a plant secondary metabolite, which shows antioxidant activity and is commonly found in many plant-based foods and beverages. Recent evidence suggests that oxidative stress contributes to the development of many human chronic diseases, including cardiovascular and neurodegenerative pathologies, metabolic syndrome, type 2 diabetes and cancer. GA and its derivative, methyl-3-O-methyl gallate (M3OMG), possess physiological and pharmacological activities closely related to their antioxidant properties. This paper describes the antidepressive-like effects of intraperitoneal administration of GA and two synthetic analogues, M3OMG and P3OMG (propyl-3-O-methylgallate), in balb/c mice with post-stroke depression, a secondary form of depression that could be due to oxidative stress occurring during cerebral ischemia and the following reperfusion. Moreover, this study determined the in vivo antioxidant activity of these compounds through the evaluation of superoxide dismutase (SOD) and catalase (Cat) activity, thiobarbituric acid-reactive substances (TBARS) and reduced glutathione (GSH) levels in mouse brain. GA and its synthetic analogues were found to be active (at doses of 25 and 50 mg/kg) in the modulation of depressive symptoms and the reduction of oxidative stress, restoring normal behavior and, at least in part, antioxidant endogenous defenses, with M3OMG being the most active of these compounds. SOD, TBARS, and GSH all showed strong correlation with behavioral parameters, suggesting that oxidative stress is tightly linked to the pathological processes involved in stroke and PSD. As a whole, the obtained results show that the administration of GA, M3OMG and P3OMG induce a reduction in depressive symptoms and oxidative stress. PMID:27136579

Identification and characterization of dwarf 62, a loss-of-function mutation in DLT/OsGRAS-32 affecting gibberellin metabolism in rice.

PubMed

Li, Wenqiang; Wu, Jianguo; Weng, Shili; Zhang, Yujiang; Zhang, Dapeng; Shi, Chunhai

2010-11-01

A dwarf mutant, dwarf 62 (d62), was isolated from rice cultivar 93-11 by mutagenesis with γ-rays. Under normal growth conditions, the mutant had multiple abnormal phenotypes, such as dwarfism, wide and dark-green leaf blades, reduced tiller numbers, late and asynchronous heading, short roots, partial male sterility, etc. Genetic analysis indicated that the abnormal phenotypes were controlled by the recessive mutation of a single nuclear gene. Using molecular markers, the D62 gene was fine mapped in 131-kb region at the short arm of chromosome 6. Positional cloning of D62 gene revealed that it was the same locus as DLT/OsGRAS-32, which encodes a member of the GRAS family. In previous studies, the DLT/OsGRAS-32 is confirmed to play positive roles in brassinosteroid (BR) signaling. Sequence analysis showed that the d62 carried a 2-bp deletion in ORF region of D62 gene which led to a loss-of-function mutation. The function of D62 gene was confirmed by complementation experiment. RT-PCR analysis and promoter activity analysis showed that the D62 gene expressed in all tested tissues including roots, stems, leaves and panicles of rice plant. The d62 mutant exhibited decreased activity of α-amylase in endosperm and reduced content of endogenous GA(1). The expression levels of gibberellin (GA) biosynthetic genes including OsCPS1, OsKS1, OsKO1, OsKAO, OsGA20ox2/SD1 and OsGA2ox3 were significantly increased in d62 mutant. Briefly, these results demonstrated that the D62 (DLT/OsGRAS-32) not only participated in the regulation of BR signaling, but also influenced GA metabolism in rice.

Gibberellins regulate the stem elongation rate without affecting the mature plant height of a quick development mutant of winter wheat (Triticum aestivum L.).

PubMed

Zhang, Ning; Xie, Yong-Dun; Guo, Hui-Jun; Zhao, Lin-Shu; Xiong, Hong-Chun; Gu, Jia-Yu; Li, Jun-Hui; Kong, Fu-Quan; Sui, Li; Zhao, Zi-Wei; Zhao, Shi-Rong; Liu, Lu-Xiang

2016-10-01

Gibberellin (GA) is essential for determining plant height. Alteration of GA content or GA signaling results in a dwarf or slender phenotype. Here, we characterized a novel wheat mutant, quick development (qd), in which GA regulates stem elongation but does not affect mature plant height. qd and wild-type plants did not exhibit phenotypic differences at the seedling stage. From jointing to heading stage, qd plants were taller than wild-type plants due to elongated cells. However, wild-type and qd plants were the same height at heading. Unlike wild-type plants, qd plants were sensitive to exogenous GA due to mutation of Rht-B1. With continuous GA stimulation, qd seedlings and adult plants were taller than wild-type. Thus, the GA content of qd plants might differ from that of wild-type during the growth process. Analysis of GA biosynthetic gene expression verified this hypothesis and showed that TaKAO, which is involved in catalyzing the early steps of GA biosynthesis, was differentially expressed in qd plants compared with wild-type. The bioactive GA associated gene TaGA20ox was downregulated in qd plants during the late growth stages. Measurements of endogenous GA content were consistent with the gene-expression analysis results. Consistent with the GA content variation, the first three basal internodes were longer and the last two internodes were shorter in qd than in wild-type plants. The qd mutant might be useful in dissecting the mechanism by which GA regulates stem-growing process, and it may be serve as a GA responsive semi-dwarf germplasm in breeding programs. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Localization of Hidden Insulinomas with ⁶⁸Ga-DOTA-Exendin-4 PET/CT: A Pilot Study.

PubMed

Antwi, Kwadwo; Fani, Melpomeni; Nicolas, Guillaume; Rottenburger, Christof; Heye, Tobias; Reubi, Jean Claude; Gloor, Beat; Christ, Emanuel; Wild, Damian

2015-07-01

(111)In-DOTA-exendin-4 SPECT/CT has been shown to be highly efficient in the detection of insulinomas. We aimed at determining whether novel PET/CT imaging with [Nle(14),Lys(40)(Ahx-DOTA-(68)Ga)NH2]exendin-4 ((68)Ga-DOTA-exendin-4) is feasible and sensitive in detecting benign insulinomas. (68)Ga-DOTA-exendin-4 PET/CT and (111)In-DOTA-exendin-4 SPECT/CT were performed in a randomized cross-over order on 5 patients with endogenous hyperinsulinemic hypoglycemia. The gold standard for comparison was the histologic diagnosis after surgery. In 4 patients histologic diagnosis confirmed a benign insulinoma, whereas one patient refused surgery despite a positive (68)Ga-DOTA-exendin-4 PET/CT scan. In 4 of 5 patients, previously performed conventional imaging (CT or MR imaging) was not able to localize the insulinoma. (68)Ga-DOTA-exendin-4 PET/CT correctly identified the insulinoma in 4 of 4 patients, whereas (111)In-DOTA-exendin-4 SPECT/CT correctly identified the insulinoma in only 2 of 4 patients. These preliminary data suggest that the use of (68)Ga-DOTA-exendin-4 PET/CT in detecting hidden insulinomas is feasible. © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

Mutation of Rice BC12/GDD1, Which Encodes a Kinesin-Like Protein That Binds to a GA Biosynthesis Gene Promoter, Leads to Dwarfism with Impaired Cell Elongation[W][OA

PubMed Central

Li, Juan; Jiang, Jiafu; Qian, Qian; Xu, Yunyuan; Zhang, Cui; Xiao, Jun; Du, Cheng; Luo, Wei; Zou, Guoxing; Chen, Mingluan; Huang, Yunqing; Feng, Yuqi; Cheng, Zhukuan; Yuan, Ming; Chong, Kang

2011-01-01

The kinesins are a family of microtubule-based motor proteins that move directionally along microtubules and are involved in many crucial cellular processes, including cell elongation in plants. Less is known about kinesins directly regulating gene transcription to affect cellular physiological processes. Here, we describe a rice (Oryza sativa) mutant, gibberellin-deficient dwarf1 (gdd1), that has a phenotype of greatly reduced length of root, stems, spikes, and seeds. This reduced length is due to decreased cell elongation and can be rescued by exogenous gibberellic acid (GA3) treatment. GDD1 was cloned by a map-based approach, was expressed constitutively, and was found to encode the kinesin-like protein BRITTLE CULM12 (BC12). Microtubule cosedimentation assays revealed that BC12/GDD1 bound to microtubules in an ATP-dependent manner. Whole-genome microarray analysis revealed the expression of ent-kaurene oxidase (KO2), which encodes an enzyme involved in GA biosynthesis, was downregulated in gdd1. Electrophoretic mobility shift and chromatin immunoprecipitation assays revealed that GDD1 bound to the element ACCAACTTGAA in the KO2 promoter. In addition, GDD1 was shown to have transactivation activity. The level of endogenous GAs was reduced in gdd1, and the reorganization of cortical microtubules was altered. Therefore, BC12/GDD1, a kinesin-like protein with transcription regulation activity, mediates cell elongation by regulating the GA biosynthesis pathway in rice. PMID:21325138

Genetic Analysis of Growth-Regulator-Induced Parthenocarpy in Arabidopsis1

PubMed Central

Vivian-Smith, Adam; Koltunow, Anna M.

1999-01-01

In Arabidopsis, seedless silique development or parthenocarpy can be induced by the application of various plant growth regulators (PGRs) to unfertilized pistils. Ecotype-specific responses were observed in the Arabidopsis ecotypes Columbia and Landsberg relative to the type of PGR and level applied. The parthenocarpic response was greatest in ecotype Landsberg, and comparisons of fruit growth and morphology were studied primarily in this ecotype. Gibberellic acid application (10 μmol pistil−1) caused development similar to that in pollinated pistils, while benzyladenine (1 μmol pistil−1) and naphthylacetic acid (10 μmol pistil−1) treatment produced shorter siliques. Naphthylacetic acid primarily modified mesocarp cell expansion. Arabidopsis mutants were employed to examine potential dependencies on gibberellin biosynthesis (ga1-3, ga4-1, and ga5-1) and perception (spy-4 and gai) during parthenocarpic silique development. Emasculated spy-4 pistils were neither obviously parthenocarpic nor deficient in PGR perception. By contrast, emasculated gai mutants did not produce parthenocarpic siliques following gibberellic acid application, but silique development occurred following pollination or application of auxin and cytokinin. Pollinated gai siliques had decreased cell numbers and morphologically resembled auxin-induced parthenocarpic siliques. This shows that a number of independent and possibly redundant pathways can direct hormone-induced parthenocarpy, and that endogenous gibberellins play a role in regulating cell expansion and promoting cell division in carpels. PMID:10517835

The Synergistic Priming Effect of Exogenous Salicylic Acid and H2O2 on Chilling Tolerance Enhancement during Maize (Zea mays L.) Seed Germination

PubMed Central

Li, Zhan; Xu, Jungui; Gao, Yue; Wang, Chun; Guo, Genyuan; Luo, Ying; Huang, Yutao; Hu, Weimin; Sheteiwy, Mohamed S.; Guan, Yajing; Hu, Jin

2017-01-01

Chilling stress is an important constraint for maize seedling establishment in the field. To examine the role of salicylic acid (SA) and hydrogen peroxide (H2O2) in response to chilling stress, we investigated the effects of seed priming with SA, H2O2, and SA+H2O2 combination on maize resistance under chilling stress (13°C). Priming with SA, H2O2, and especially SA+H2O2 shortened seed germination time and enhanced seed vigor and seedling growth as compared with hydropriming and non-priming treatments under low temperature. Meanwhile, SA+H2O2 priming notably increased the endogenous H2O2 and SA content, antioxidant enzymes activities and their corresponding genes ZmPAL, ZmSOD4, ZmAPX2, ZmCAT2, and ZmGR expression levels. The α-amylase activity was enhanced to mobilize starch to supply metabolites such as soluble sugar and energy for seed germination under chilling stress. In addition, the SA+H2O2 combination positively up-regulated expressions of gibberellic acid (GA) biosynthesis genes ZmGA20ox1 and ZmGA3ox2, and down-regulated GA catabolism gene ZmGA2ox1 expression; while it promoted GA signaling transduction genes expressions of ZmGID1 and ZmGID2 and decreased the level of seed germination inhibitor gene ZmRGL2. The abscisic acid (ABA) catabolism gene ZmCYP707A2 and the expressions of ZmCPK11 and ZmSnRK2.1 encoding response receptors in ABA signaling pathway were all up-regulated. These results strongly suggested that priming with SA and H2O2 synergistically promoted hormones metabolism and signal transduction, and enhanced energy supply and antioxidant enzymes activities under chilling stress, which were closely relevant with chilling injury alleviation and chilling-tolerance improvement in maize seed. Highlights:Seed germination and seedling growth were significantly improved under chilling stress by priming with SA+H2O2 combination, which was closely relevant with the change of reactive oxygen species, metabolites and energy supply, hormones metabolism and regulation. PMID:28725229

68Ga/177Lu-labeled DOTA-TATE shows similar imaging and biodistribution in neuroendocrine tumor model.

PubMed

Liu, Fei; Zhu, Hua; Yu, Jiangyuan; Han, Xuedi; Xie, Qinghua; Liu, Teli; Xia, Chuanqin; Li, Nan; Yang, Zhi

2017-06-01

Somatostatin receptors are overexpressed in neuroendocrine tumors, whose endogenous ligands are somatostatin. DOTA-TATE is an analogue of somatostatin, which shows high binding affinity to somatostatin receptors. We aim to evaluate the 68 Ga/ 177 Lu-labeling DOTA-TATE kit in neuroendocrine tumor model for molecular imaging and to try human-positron emission tomography/computed tomography imaging of 68 Ga-DOTA-TATE in neuroendocrine tumor patients. DOTA-TATE kits were formulated and radiolabeled with 68 Ga/ 177 Lu for 68 Ga/ 177 Lu-DOTA-TATE (M-DOTA-TATE). In vitro and in vivo stability of 177 Lu-DOTA-TATE were performed. Nude mice bearing human tumors were injected with 68 Ga-DOTA-TATE or 177 Lu-DOTA-TATE for micro-positron emission tomography and micro-single-photon emission computed tomography/computed tomography imaging separately, and clinical positron emission tomography/computed tomography images of 68 Ga-DOTA-TATE were obtained at 1 h post-intravenous injection from patients with neuroendocrine tumors. Micro-positron emission tomography and micro-single-photon emission computed tomography/computed tomography imaging of 68 Ga-DOTA-TATE and 177 Lu-DOTA-TATE both showed clear tumor uptake which could be blocked by excess DOTA-TATE. In addition, 68 Ga-DOTA-TATE-positron emission tomography/computed tomography imaging in neuroendocrine tumor patients could show primary and metastatic lesions. 68 Ga-DOTA-TATE and 177 Lu-DOTA-TATE could accumulate in tumors in animal models, paving the way for better clinical peptide receptor radionuclide therapy for neuroendocrine tumor patients in Asian population.

The ontogeny of insulin signaling in the preterm baboon model.

PubMed

Blanco, Cynthia L; Liang, Hanyu; Joya-Galeana, Joaquin; DeFronzo, Ralph A; McCurnin, Donald; Musi, Nicolas

2010-05-01

Hyperglycemia, a prevalent condition in premature infants, is thought to be a consequence of incomplete suppression of endogenous glucose production and reduced insulin-stimulated glucose disposal in peripheral tissues. However, the molecular basis for these conditions remains unclear. To test the hypothesis that the insulin transduction pathway is underdeveloped with prematurity, fetal baboons were delivered, anesthetized, and euthanized at 125 d gestational age (GA), 140 d GA, or near term at 175 d GA. Vastus lateralis muscle and liver tissues were obtained, and protein content of insulin signaling molecules [insulin receptor (IR)-beta, IR substate-1, p85 subunit of phosphatidylinositol 3-kinase, Akt, and AS160] and glucose transporters (GLUT)-1 and GLUT4 was measured by Western blotting. Muscle from 125 d GA baboons had markedly reduced GLUT1 protein content (16% of 140 d GA and 9% of 175 d GA fetuses). GLUT4 and AS160 also were severely reduced in 125 d GA fetal muscle (43% of 175 d GA and 35% of 175 d GA, respectively). In contrast, the protein content of IR-beta, IR substate-1, and Akt was elevated by 1.7-, 5.2-, and 1.9-fold, respectively, in muscle from 125 d GA baboons when compared with 175 d GA fetuses. No differences were found in the content of insulin signaling proteins in liver. In conclusion, significant gestational differences exist in the protein content of several insulin signaling proteins in the muscle of fetal baboons. Reduced muscle content of key glucose transport-regulating proteins (GLUT1, GLUT4, AS160) could play a role in the pathogenesis of neonatal hyperglycemia and reduced insulin-stimulated glucose disposal.

Association between CYP2E1 polymorphisms and risk of differentiated thyroid carcinoma.

PubMed

Pellé, Lucia; Cipollini, Monica; Tremmel, Roman; Romei, Cristina; Figlioli, Gisella; Gemignani, Federica; Melaiu, Ombretta; De Santi, Chiara; Barone, Elisa; Elisei, Rossella; Seiser, Eric; Innocenti, Federico; Zanger, Ulrich M; Landi, Stefano

2016-12-01

Differentiated thyroid carcinoma (DTC) results from complex interactions between genetic and environmental factors. Known etiological factors include exposure to ionizing radiations, previous thyroid diseases, and hormone factors. It has been speculated that dietary acrylamide (AA) formed in diverse foods following the Maillard's reaction could be a contributing factor for DTC in humans. Upon absorption, AA is biotransformed mainly by cytochrome P450 2E1 (CYP2E1) to glycidamide (GA). Considering that polymorphisms within CYP2E1 were found associated with endogenous levels of AA-Valine and GA-Valine hemoglobin adducts in humans, we raised the hypothesis that specific CYP2E1 genotypes could be associated with the risk of DTC. Analysis of four haplotype tagging SNPs (ht-SNPs) within the locus in a discovery case-control study (N = 350/350) indicated an association between rs2480258 and DTC risk. This ht-SNP resides within a linkage disequilibrium block spanning intron VIII and the 3'-untranslated region. Extended analysis in a large replication set (2429 controls and 767 cases) confirmed the association, with odds ratios for GA and AA genotypes of 1.24 (95 % confidence interval (CI) 1.03-1.48) and 1.56 (95 % CI, 1.06-2.30), respectively. Functionally, the minor allele was associated with low levels of CYP2E1 mRNA and protein expression as well as lower enzymatic activity in a series of 149 human liver samples. Our data support the hypothesis that inter-individual differences in CYP2E1 activity could modulate the risk of developing DTC suggesting that the exposure to specific xenobiotics, such as AA, could play a role in this process.

An A20/AN1-type zinc finger protein modulates gibberellins and abscisic acid contents and increases sensitivity to abiotic stress in rice (Oryza sativa).

PubMed

Zhang, Ye; Lan, Hongxia; Shao, Qiaolin; Wang, Ruqin; Chen, Hui; Tang, Haijuan; Zhang, Hongsheng; Huang, Ji

2016-01-01

The plant hormones gibberellins (GA) and abscisic acid (ABA) play important roles in plant development and stress responses. Here we report a novel A20/AN1-type zinc finger protein ZFP185 involved in GA and ABA signaling in the regulation of growth and stress response. ZFP185 was constitutively expressed in various rice tissues. Overexpression of ZFP185 in rice results in a semi-dwarfism phenotype, reduced cell size, and the decrease of endogenous GA3 content. By contrast, higher GA3 content was observed in RNAi plants. The application of exogenous GA3 can fully rescue the semi-dwarfism phenotype of ZFP185 overexpressing plants, suggesting the negative role of ZFP185 in GA biosynthesis. Besides GA, overexpression of ZFP185 decreased ABA content and expression of several ABA biosynthesis-related genes. Moreover, it was found that ZFP185, unlike previously known A20/AN1-type zinc finger genes, increases sensitivity to drought, cold, and salt stresses, implying the negative role of ZFP185 in stress tolerance. ZFP185 was localized in the cytoplasm and lacked transcriptional activation potential. Our study suggests that ZFP185 regulates plant growth and stress responses by affecting GA and ABA biosynthesis in rice. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Molecular imaging analysis of intestinal insulin absorption boosted by cell-penetrating peptides by using positron emission tomography.

PubMed

Kamei, Noriyasu; Morishita, Mariko; Kanayama, Yousuke; Hasegawa, Koki; Nishimura, Mie; Hayashinaka, Emi; Wada, Yasuhiro; Watanabe, Yasuyoshi; Takayama, Kozo

2010-08-17

Molecular imaging technique by use of positron emission tomography (PET) is a noninvasive tool that allows one to quantitatively analyze the function of endogenous molecules and the pharmacokinetics of therapeutic agents in vivo. This technique is expected to be useful for evaluating the effectiveness of diverse drug delivery systems. We demonstrated previously that intestinal insulin absorption is increased significantly by coadministration of cell-penetrating peptides (CPPs), which are taken up effectively by several cells. However, the distribution behavior of insulin whose absorption is increased by CPPs is not clear. We used PET imaging and quantitatively analyzed the intestinal absorption and subsequent distribution of insulin and the effect of CPPs on its absorption and distribution. An unlabeled insulin solution containing tracer insulin, (68)Ga-DOTA-insulin, was administered with or without CPPs into a rat ileal closed loop. PET imaging showed that the CPPs, particularly D-R8 and L-penetratin, significantly increased the (68)Ga-DOTA-insulin level in the liver, kidney, and circulation. After absorption from the intestine, the (68)Ga-DOTA-insulin passed rapidly through the liver and accumulated in the kidney. The increase in the hepatic and renal distribution of (68)Ga-DOTA-insulin by each CPP coadministration was similar manner as that in intestinal absorption, suggesting that the increased accumulation of insulin in the liver and kidney induced by coadministration of CPPs was associated with the increased intestinal absorption of insulin. This is the first study to show that PET imaging enables one to quantitatively analyze the distribution behavior of intestinally absorbed insulin in several organs. This imaging methodology is likely to be useful for developing effective drug delivery systems targeted to specific organs. Copyright 2010 Elsevier B.V. All rights reserved.

Altered Pre-mRNA Splicing Caused by a Novel Intronic Mutation c.1443+5G>A in the Dihydropyrimidinase (DPYS) Gene

PubMed Central

Nakajima, Yoko; Meijer, Judith; Zhang, Chunhua; Wang, Xu; Kondo, Tomomi; Ito, Tetsuya; Dobritzsch, Doreen; Van Kuilenburg, André B. P.

2016-01-01

Dihydropyrimidinase (DHP) deficiency is an autosomal recessive disease caused by mutations in the DPYS gene. Patients present with highly elevated levels of dihydrouracil and dihydrothymine in their urine, blood and cerebrospinal fluid. The analysis of the effect of mutations in DPYS on pre-mRNA splicing is hampered by the fact that DHP is primarily expressed in liver and kidney cells. The minigene approach can detect mRNA splicing aberrations using cells that do not express the endogenous mRNA. We have used a minigene-based approach to analyze the effects of a presumptive pre-mRNA splicing mutation in two newly identified Chinese pediatric patients with DHP deficiency. Mutation analysis of DPYS showed that both patients were compound heterozygous for a novel intronic mutation c.1443+5G>A in intron 8 and a previously described missense mutation c.1001A>G (p.Q334R) in exon 6. Wild-type and the mutated minigene constructs, containing exons 7, 8 and 9 of DPYS, yielded different splicing products after expression in HEK293 cells. The c.1443+5G>A mutation resulted in altered pre-mRNA splicing of the DPYS minigene construct with full skipping of exon 8. Analysis of the DHP crystal structure showed that the deletion of exon 8 severely affects folding, stability and homooligomerization of the enzyme as well as disruption of the catalytic site. Thus, the analysis suggests that the c.1443+5G>A mutation results in aberrant splicing of the pre-mRNA encoding DHP, underlying the DHP deficiency in two unrelated Chinese patients. PMID:26771602

Altered Pre-mRNA Splicing Caused by a Novel Intronic Mutation c.1443+5G>A in the Dihydropyrimidinase (DPYS) Gene.

PubMed

Nakajima, Yoko; Meijer, Judith; Zhang, Chunhua; Wang, Xu; Kondo, Tomomi; Ito, Tetsuya; Dobritzsch, Doreen; Van Kuilenburg, André B P

2016-01-12

Dihydropyrimidinase (DHP) deficiency is an autosomal recessive disease caused by mutations in the DPYS gene. Patients present with highly elevated levels of dihydrouracil and dihydrothymine in their urine, blood and cerebrospinal fluid. The analysis of the effect of mutations in DPYS on pre-mRNA splicing is hampered by the fact that DHP is primarily expressed in liver and kidney cells. The minigene approach can detect mRNA splicing aberrations using cells that do not express the endogenous mRNA. We have used a minigene-based approach to analyze the effects of a presumptive pre-mRNA splicing mutation in two newly identified Chinese pediatric patients with DHP deficiency. Mutation analysis of DPYS showed that both patients were compound heterozygous for a novel intronic mutation c.1443+5G>A in intron 8 and a previously described missense mutation c.1001A>G (p.Q334R) in exon 6. Wild-type and the mutated minigene constructs, containing exons 7, 8 and 9 of DPYS, yielded different splicing products after expression in HEK293 cells. The c.1443+5G>A mutation resulted in altered pre-mRNA splicing of the DPYS minigene construct with full skipping of exon 8. Analysis of the DHP crystal structure showed that the deletion of exon 8 severely affects folding, stability and homooligomerization of the enzyme as well as disruption of the catalytic site. Thus, the analysis suggests that the c.1443+5G>A mutation results in aberrant splicing of the pre-mRNA encoding DHP, underlying the DHP deficiency in two unrelated Chinese patients.

Degradation effect of diepoxide fixation on porcine endogenous retrovirus DNA in heart valves: molecular aspects.

PubMed

Cyganek-Niemiec, Aleksandra; Strzalka-Mrozik, Barbara; Pawlus-Lachecka, Lucyna; Wszolek, Jolanta; Adamska, Jolanta; Kudrjavtseva, Julia; Zhuravleva, Irina; Kimsa, Malgorzata; Okla, Hubert; Kimsa, Magdalena; Gudek, Agnieszka; Mazurek, Urszula

2012-01-01

Xenotransplantations of porcine cells, tissues, and organs involve a risk of zoonotic viral infections in recipients, including by porcine endogenous retroviruses (PERVs), which are embedded the genome of all pigs. An appropriate preparation of porcine heart valves for transplantation can prevent retroviral infection. Therefore, the present study focuses on the effect of epoxy compounds and glutaraldehyde on the PERV presence in porcine heart valves prepared for clinical use. Porcine aortic heart valves were fixed with ethylene glycol diglycidyl ether (EDGE) at 5 °C and 25 °C as well as with glutaraldehyde (GA) for 4 weeks. Salting out was used to isolate genomic DNA from native as well as EDGE- and GA-fixed fragments of valves every week. Quantification of PERV-A, PERV-B, and PERV-C DNA was performed by real-time quantitative polymerase chain reaction (QPCR). All subtypes of PERVs were detected in native porcine aortic heart valves. The reduction of the PERV-A, PERV-B, and PERV-C DNA copy numbers was observed in the heart valves which were EDGE-fixed at both temperatures, and in GA-fixed ones in the following weeks. After 7 and 14 days of EDGE cross-linking, significant differences between the investigated temperatures were found for the number of PERV-A and PERV-B copies. PERV DNA was completely degraded within the first week of EDGE fixation at 25 °C. EDGE fixation induces complete PERV genetic material degradation in porcine aortic heart valves. This suggests that epoxy compounds may be alternatively used in the preparation of bioprosthetic heart valves in future.

Transspecies Transmission of Gammaretroviruses and the Origin of the Gibbon Ape Leukaemia Virus (GaLV) and the Koala Retrovirus (KoRV).

PubMed

Denner, Joachim

2016-12-20

Transspecies transmission of retroviruses is a frequent event, and the human immunodeficiency virus-1 (HIV-1) is a well-known example. The gibbon ape leukaemia virus (GaLV) and koala retrovirus (KoRV), two gammaretroviruses, are also the result of a transspecies transmission, however from a still unknown host. Related retroviruses have been found in Southeast Asian mice although the sequence similarity was limited. Viruses with a higher sequence homology were isolated from Melomys burtoni , the Australian and Indonesian grassland melomys. However, only the habitats of the koalas and the grassland melomys in Australia are overlapping, indicating that the melomys virus may not be the precursor of the GaLV. Viruses closely related to GaLV/KoRV were also detected in bats. Therefore, given the fact that the habitats of the gibbons in Thailand and the koalas in Australia are far away, and that bats are able to fly over long distances, the hypothesis that retroviruses of bats are the origin of GaLV and KoRV deserves consideration. Analysis of previous transspecies transmissions of retroviruses may help to evaluate the potential of transmission of related retroviruses in the future, e.g., that of porcine endogenous retroviruses (PERVs) during xenotransplantation using pig cells, tissues or organs.

Search for infective mammalian type-C virus-related genes in the DNA of human sarcomas and leukemias.

PubMed

Nicolson, M O; Gilden, R V; Charman, H; Rice, N; Heberling, R; McAllister, R M

1978-06-15

DNA was extracted from two human sarcoma cell lines, TE-32 and TE-418, and the leukemic cells from five children with acute myelocytic leukemia, three children with acute lymphocytic leukemia and four adults with acute myelocytic leukemia. The DNAs, assayed for infectivity by transfection techniques, induced no measurable virus by methods which would detect known mammalian C-type antigens or RNA-directed DNA polymerase in TE-32, D-17 dog cells and other indicator cells, nor did they recombine with or rescue endogenous human or exogenous murine or baboon type-C virus. Model systems used as controls were human sarcoma cells, TE-32 and HT-1080, and human lymphoma cells TE-543, experimentally infected with KiMuLV, GaLV or baboon type-C virus, all of which released infectious virus and whose DNAs were infectious for TE-32 and D-17 dog cells. Other model systems included two baboon placentas and one embryonic cell strain spontaneously releasing infectious endogenous baboon virus and yielding DNAs infectious for D-17 dog cells but not for TE-32 cells. Four other baboon embryonic tissues and two embryonic cell strains, releasing either low levels of virus or no virus, did not yield infectious DNA.

A preliminary analysis of the effects of bisphenol A on the plant root growth via changes in endogenous plant hormones.

PubMed

Li, Xingyi; Wang, Lihong; Wang, Shengman; Yang, Qing; Zhou, Qing; Huang, Xiaohua

2018-04-15

Bisphenol A (BPA) is ubiquitous in the environment worldwide, affecting plant growth and development. Endogenous plant hormones serve as switches that regulate plant growth and development. However, plants have different physiological requirements and environmental adaptive capacities during the different growth stages. Here, we investigated the effects of BPA on soybean (Glycine max L.) root growth at the three growth stages and analyzed the mechanisms underlying the effects of BPA on the root growth by assessing changes in endogenous hormone. The results showed that low concentration of BPA (1.5mgL -1 ) improved root growth (except at the seed-filling stage), increased indole-3-acetic acid (IAA) content at the first two growth stages, and increased zeatin (ZT) content and decreased gibberellic acid (GA 3 ) content at the seedling stage. But low concentration of BPA caused decreased ethylene (ETH) contents and constant abscisic acid (ABA) content at all three stages. However, BPA at moderate and high concentrations (6.0 and 12.0mgL -1 ) inhibited root growth, causing the decreased IAA, GA 3 and ETH contents and increased ABA content at all three growth stages. The change degrees of above indices were weakened with prolonging the growth stages. After BPA withdrawal, both the root growth and the hormone contents recovered (with the exception of ZT and ETH), and the recovery degrees had negative correlation with the BPA exposure concentration and had positive correlation with the growth stage. Changes in residual BPA content in the roots were also observed at different BPA concentrations and different growth stages. Our results demonstrated the effects of BPA on root growth were related to BPA-induced changes in hormone, which performed differently at various growth stages. Copyright © 2017 Elsevier Inc. All rights reserved.

Effects of chilling and ABA on (/sup 3/H)gibberellin A/sub 4/ metabolism in somatic embryos of grape (Vitis vinifera L. x V. rupestris Scheele)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pearce, D.; Pharis, R.P.; Rajasekaran, K.

1987-06-01

Previous work has indicated that changes in gibberellin (GA) metabolism may be involved in chilling-induced release from dormancy in somatic embryos of grape (Vitis vinifera L. x V. rupestris Scheele). The authors have chilled somatic embryos of grape for 2, 4, or 8 weeks, then incubated them with (/sup 3/H)GA/sub 4/ (of high specific activity, 4.81 x 10/sup 19/ becquerel per millimole) for 48 hours at 26/sup 0/C. Chilling had little effect on the total amount of free (/sup 3/H)GA-like metabolites formed during incubation at 26/sup 0/C, but did change the relative proportions of individual metabolites. The amount of highlymore » water-soluble (/sup 3/H) metabolites formed at 26/sup 0/C decreased in embryos chilled for 4 or 8 weeks. The concentration of endogeneous GA precursors (e.g., GA/sub 12/ aldehyde-, kaurene, and kaurenoic acid-like substances) increased in embryos chilled for 4 or 8 weeks. Treatment with abscisic acid (ABA) (known to inhibit germination in grape embryos) concurrent with (/sup 3/H)GA/sub 4/ treatment at 26/sup 0/C, reduced the uptake of (/sup 3/H) GA/sub 4/ but had little effect on the qualitative spectrum of metabolites. However, in the embryos chilled for 8 weeks and then treated with ABA for 48 hours at 26/sup 0/C, there was a higher concentration of GA precursors than in untreated control embryos. Chilled embryos thus have an enhanced potential for an increase in free GAs through synthesis from increased amounts of GA precursors, or through a reduced ability to form highly water-soluble GA metabolites (i.e., GA conjugates or polyhydroxylated free GAs).« less

Gaussian Accelerated Molecular Dynamics in NAMD

PubMed Central

2016-01-01

Gaussian accelerated molecular dynamics (GaMD) is a recently developed enhanced sampling technique that provides efficient free energy calculations of biomolecules. Like the previous accelerated molecular dynamics (aMD), GaMD allows for “unconstrained” enhanced sampling without the need to set predefined collective variables and so is useful for studying complex biomolecular conformational changes such as protein folding and ligand binding. Furthermore, because the boost potential is constructed using a harmonic function that follows Gaussian distribution in GaMD, cumulant expansion to the second order can be applied to recover the original free energy profiles of proteins and other large biomolecules, which solves a long-standing energetic reweighting problem of the previous aMD method. Taken together, GaMD offers major advantages for both unconstrained enhanced sampling and free energy calculations of large biomolecules. Here, we have implemented GaMD in the NAMD package on top of the existing aMD feature and validated it on three model systems: alanine dipeptide, the chignolin fast-folding protein, and the M3 muscarinic G protein-coupled receptor (GPCR). For alanine dipeptide, while conventional molecular dynamics (cMD) simulations performed for 30 ns are poorly converged, GaMD simulations of the same length yield free energy profiles that agree quantitatively with those of 1000 ns cMD simulation. Further GaMD simulations have captured folding of the chignolin and binding of the acetylcholine (ACh) endogenous agonist to the M3 muscarinic receptor. The reweighted free energy profiles are used to characterize the protein folding and ligand binding pathways quantitatively. GaMD implemented in the scalable NAMD is widely applicable to enhanced sampling and free energy calculations of large biomolecules. PMID:28034310

Gaussian Accelerated Molecular Dynamics in NAMD.

PubMed

Pang, Yui Tik; Miao, Yinglong; Wang, Yi; McCammon, J Andrew

2017-01-10

Gaussian accelerated molecular dynamics (GaMD) is a recently developed enhanced sampling technique that provides efficient free energy calculations of biomolecules. Like the previous accelerated molecular dynamics (aMD), GaMD allows for "unconstrained" enhanced sampling without the need to set predefined collective variables and so is useful for studying complex biomolecular conformational changes such as protein folding and ligand binding. Furthermore, because the boost potential is constructed using a harmonic function that follows Gaussian distribution in GaMD, cumulant expansion to the second order can be applied to recover the original free energy profiles of proteins and other large biomolecules, which solves a long-standing energetic reweighting problem of the previous aMD method. Taken together, GaMD offers major advantages for both unconstrained enhanced sampling and free energy calculations of large biomolecules. Here, we have implemented GaMD in the NAMD package on top of the existing aMD feature and validated it on three model systems: alanine dipeptide, the chignolin fast-folding protein, and the M 3 muscarinic G protein-coupled receptor (GPCR). For alanine dipeptide, while conventional molecular dynamics (cMD) simulations performed for 30 ns are poorly converged, GaMD simulations of the same length yield free energy profiles that agree quantitatively with those of 1000 ns cMD simulation. Further GaMD simulations have captured folding of the chignolin and binding of the acetylcholine (ACh) endogenous agonist to the M 3 muscarinic receptor. The reweighted free energy profiles are used to characterize the protein folding and ligand binding pathways quantitatively. GaMD implemented in the scalable NAMD is widely applicable to enhanced sampling and free energy calculations of large biomolecules.

Recombinant DNA modification of gibberellin metabolism alters growth rate and biomass allocation in Populus

DOE PAGES

Lu, Haiwei; Viswanath, Venkatesh; Ma, Cathleen; ...

2015-11-13

Overexpression of genes that modify gibberellin (GA) metabolism and signaling have been previously shown to produce trees with improved biomass production but highly disturbed development. In order to examine if more subtle types of genetic modification of GA could improve growth rate and modify tree architecture, we transformed a model poplar genotype (Populus tremula × P. alba) with eight genes, including two cisgenes (intact copies of native genes), four intragenes (modified copies of native genes), and two transgenes (from sexually incompatible species), and studied their effects under greenhouse and field conditions. In the greenhouse, four out of the eight testedmore » genes produced a significant and often striking improvement of stem volume, and two constructs significantly modified the proportion of root or shoot biomass. Characterization of GA concentrations in the cisgenic population that had an additional copy of a poplar GA20-oxidase gene showed elevated concentrations of 13-hydroxylated GAs compared to wild-type poplars. In the field, we observed growth improvement for three of the six tested constructs, but it was significantly greater for only one of the constructs, a pRGL:GA20-oxidase intragene. The greenhouse and field responses were highly variable, possibly to due to cross-talk among the GA pathway and other stress response pathways, or due to interactions between the cisgenes and intragenes with highly similar endogenes. Our results indicate that extensive field trials, similar to those required for conventional breeding, will be critical to evaluating the value and pleiotropic effects of GA-modifying genes.« less

Recombinant DNA modification of gibberellin metabolism alters growth rate and biomass allocation in Populus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Haiwei; Viswanath, Venkatesh; Ma, Cathleen

Overexpression of genes that modify gibberellin (GA) metabolism and signaling have been previously shown to produce trees with improved biomass production but highly disturbed development. In order to examine if more subtle types of genetic modification of GA could improve growth rate and modify tree architecture, we transformed a model poplar genotype (Populus tremula × P. alba) with eight genes, including two cisgenes (intact copies of native genes), four intragenes (modified copies of native genes), and two transgenes (from sexually incompatible species), and studied their effects under greenhouse and field conditions. In the greenhouse, four out of the eight testedmore » genes produced a significant and often striking improvement of stem volume, and two constructs significantly modified the proportion of root or shoot biomass. Characterization of GA concentrations in the cisgenic population that had an additional copy of a poplar GA20-oxidase gene showed elevated concentrations of 13-hydroxylated GAs compared to wild-type poplars. In the field, we observed growth improvement for three of the six tested constructs, but it was significantly greater for only one of the constructs, a pRGL:GA20-oxidase intragene. The greenhouse and field responses were highly variable, possibly to due to cross-talk among the GA pathway and other stress response pathways, or due to interactions between the cisgenes and intragenes with highly similar endogenes. Our results indicate that extensive field trials, similar to those required for conventional breeding, will be critical to evaluating the value and pleiotropic effects of GA-modifying genes.« less

Effects of theobroxide, a natural product, on the level of endogenous jasmonoids.

PubMed

Yang, Qing; Gao, Xiquan; Fujino, Yumiko; Matsuura, Hideyuki; Yoshihara, Teruhiko

2004-01-01

The natural potato microtuber inducing substance, theobroxide, strongly induces the formation of tuber of potato (Solanum tuberosum L.) and flower bud of morning glory (Pharbitis nil) plants under non-inducing conditions (long days) (Yoshihara et al., 2000). In the present study, theobroxide was evaluated for its effect on the level of endogenous jasmonoids in different tissues of such two plants. An in vitro bioassay using cultures of single-node segments of potato stems was performed with the supplement of theobroxide in the medium. The endogenous jasmonic acid (JA) and its analogue tuberonic acid (TA, 12-hydroxyjasmonic acid) in segments and microtubers were quantitatively analyzed. The increase in the endogenous JA level caused by theobroxide was observed in both segments and microtubers. Endogenous TA was only detected in segments, and the content increased with the concentration of theobroxide. As for morning glory, the whole plant was sprayed with theobroxide for 1 approximately 5 weeks under different photoperiods and endogenous JA in the leaves was quantitatively analyzed. Theobroxide spraying increased the level of endogenous JA in the leaves of the plants grown under both long and short days.

The APETALA-2-like transcription factor OsAP2-39 controls key interactions between abscisic acid and gibberellin in rice.

PubMed

Yaish, Mahmoud W; El-Kereamy, Ashraf; Zhu, Tong; Beatty, Perrin H; Good, Allen G; Bi, Yong-Mei; Rothstein, Steven J

2010-09-09

The interaction between phytohormones is an important mechanism which controls growth and developmental processes in plants. Deciphering these interactions is a crucial step in helping to develop crops with enhanced yield and resistance to environmental stresses. Controlling the expression level of OsAP2-39 which includes an APETALA 2 (AP2) domain leads to phenotypic changes in rice. Overexpression of OsAP2-39 leads to a reduction in yield by decreasing the biomass and the number of seeds in the transgenic rice lines. Global transcriptome analysis of the OsAP2-39 overexpression transgenic rice revealed the upregulation of a key abscisic acid (ABA) biosynthetic gene OsNCED-I which codes for 9-cis-epoxycarotenoid dioxygenase and leads to an increase in the endogenous ABA level. In addition to OsNCED-1, the gene expression analysis revealed the upregulation of a gene that codes for the Elongation of Upper most Internode (EUI) protein, an enzyme that catalyzes 16α, 17-epoxidation of non-13-hydroxylated GAs, which has been shown to deactivate gibberellins (GAs) in rice. The exogenous application of GA restores the wild-type phenotype in the transgenic line and ABA application induces the expression of EUI and suppresses the expression of OsAP2-39 in the wild-type line. These observations clarify the antagonistic relationship between ABA and GA and illustrate a mechanism that leads to homeostasis of these hormones. In vivo and in vitro analysis showed that the expression of both OsNCED-1 and EUI are directly controlled by OsAP2-39. Together, these results reveal a novel mechanism for the control of the ABA/GA balance in rice which is regulated by OsAP2-39 that in turn regulates plant growth and seed production.

The APETALA-2-Like Transcription Factor OsAP2-39 Controls Key Interactions between Abscisic Acid and Gibberellin in Rice

PubMed Central

Yaish, Mahmoud W.; El-kereamy, Ashraf; Zhu, Tong; Beatty, Perrin H.; Good, Allen G.; Bi, Yong-Mei; Rothstein, Steven J.

2010-01-01

The interaction between phytohormones is an important mechanism which controls growth and developmental processes in plants. Deciphering these interactions is a crucial step in helping to develop crops with enhanced yield and resistance to environmental stresses. Controlling the expression level of OsAP2-39 which includes an APETALA 2 (AP2) domain leads to phenotypic changes in rice. Overexpression of OsAP2-39 leads to a reduction in yield by decreasing the biomass and the number of seeds in the transgenic rice lines. Global transcriptome analysis of the OsAP2-39 overexpression transgenic rice revealed the upregulation of a key Abscisic Acid (ABA) biosynthetic gene OsNCED-I which codes for 9-cis-epoxycarotenoid dioxygenase and leads to an increase in the endogenous ABA level. In addition to OsNCED-1, the gene expression analysis revealed the upregulation of a gene that codes for the Elongation of Upper most Internode (EUI) protein, an enzyme that catalyzes 16α, 17-epoxidation of non-13-hydroxylated GAs, which has been shown to deactivate gibberellins (GAs) in rice. The exogenous application of GA restores the wild-type phenotype in the transgenic line and ABA application induces the expression of EUI and suppresses the expression of OsAP2-39 in the wild-type line. These observations clarify the antagonistic relationship between ABA and GA and illustrate a mechanism that leads to homeostasis of these hormones. In vivo and in vitro analysis showed that the expression of both OsNCED-1 and EUI are directly controlled by OsAP2-39. Together, these results reveal a novel mechanism for the control of the ABA/GA balance in rice which is regulated by OsAP2-39 that in turn regulates plant growth and seed production. PMID:20838584

Endophytic fungal association via gibberellins and indole acetic acid can improve plant growth under abiotic stress: an example of Paecilomyces formosus LHL10

PubMed Central

2012-01-01

Background Endophytic fungi are little known for exogenous secretion of phytohormones and mitigation of salinity stress, which is a major limiting factor for agriculture production worldwide. Current study was designed to isolate phytohormone producing endophytic fungus from the roots of cucumber plant and identify its role in plant growth and stress tolerance under saline conditions. Results We isolated nine endophytic fungi from the roots of cucumber plant and screened their culture filtrates (CF) on gibberellins (GAs) deficient mutant rice cultivar Waito-C and normal GAs biosynthesis rice cultivar Dongjin-byeo. The CF of a fungal isolate CSH-6H significantly increased the growth of Waito-C and Dongjin-byeo seedlings as compared to control. Analysis of the CF showed presence of GAs (GA1, GA3, GA4, GA8, GA9, GA12, GA20 and GA24) and indole acetic acid. The endophyte CSH-6H was identified as a strain of Paecilomyces formosus LHL10 on the basis of phylogenetic analysis of ITS sequence similarity. Under salinity stress, P. formosus inoculation significantly enhanced cucumber shoot length and allied growth characteristics as compared to non-inoculated control plants. The hypha of P. formosus was also observed in the cortical and pericycle regions of the host-plant roots and was successfully re-isolated using PCR techniques. P. formosus association counteracted the adverse effects of salinity by accumulating proline and antioxidants and maintaining plant water potential. Thus the electrolytic leakage and membrane damage to the cucumber plants was reduced in the association of endophyte. Reduced content of stress responsive abscisic acid suggest lesser stress convened to endophyte-associated plants. On contrary, elevated endogenous GAs (GA3, GA4, GA12 and GA20) contents in endophyte-associated cucumber plants evidenced salinity stress modulation. Conclusion The results reveal that mutualistic interactions of phytohormones secreting endophytic fungi can ameliorate host plant growth and alleviate adverse effects of salt stress. Such fungal strain could be used for further field trials to improve agricultural productivity under saline conditions. PMID:22235902

Characterization of genes encoding ABA 8'-hydroxylase in ethylene-induced stem growth of deepwater rice (Oryza sativa L.).

PubMed

Yang, Seung-Hwan; Choi, Dongsu

2006-11-24

Ethylene and submergence enhance stem elongation of deepwater rice, at least in part, by reducing in the internode the endogenous abscisic acid (ABA) content and increasing the level of gibberellin A1 (GA1). We cloned and characterized the CYP707A5 and CYP707A6 genes, which encode putative ABA 8'-hydroxylase, the enzyme that catalyzes the oxidation of ABA. Expression of CYP707A5 was upregulated significantly by ethylene treatment, whereas that of CYP707A6 was not altered. Recombinant proteins from both genes expressed in yeast cells showed activity of ABA 8'-hydroxylase. This finding indicates that CYP707A5 may play a role in ABA catabolism during submergence- or ethylene-induced stem elongation in deepwater rice. Taken together, these results provide links between the molecular mechanisms and physiological phenomena of submergence- and ethylene-induced stem elongation in deepwater rice.

Plant hormone signaling lightens up: integrators of light and hormones.

PubMed

Lau, On Sun; Deng, Xing Wang

2010-10-01

Light is an important environmental signal that regulates diverse growth and developmental processes in plants. In these light-regulated processes, multiple hormonal pathways are often modulated by light to mediate the developmental changes. Conversely, hormone levels in plants also serve as endogenous cues in influencing light responsiveness. Although interactions between light and hormone signaling pathways have long been observed, recent studies have advanced our understanding by identifying signaling integrators that connect the pathways. These integrators, namely PHYTOCHROME-INTERACTING FACTOR 3 (PIF3), PIF4, PIF3-LIKE 5 (PIL5)/PIF1 and LONG HYPOCOTYL 5 (HY5), are key light signaling components and they link light signals to the signaling of phytohormones, such as gibberellin (GA), abscisic acid (ABA), auxin and cytokinin, in regulating seedling photomorphogenesis and seed germination. This review focuses on these integrators in illustrating how light and hormone interact. Copyright © 2010 Elsevier Ltd. All rights reserved.

Differential hormonal and gene expression dynamics in two inbred sunflower lines with contrasting dormancy level.

PubMed

Roselló, Paula L; Vigliocco, Ana E; Andrade, Andrea M; Riera, Natalí V; Calafat, Mario; Molas, María L; Alemano, Sergio G

2016-05-01

Seed germination and dormancy are tightly regulated by hormone metabolism and signaling pathway. We investigated the endogenous content of abscisic acid (ABA), its catabolites, and gibberellins (GAs), as well as the expression level of certain ABA and GAs metabolic and signaling genes in embryo of dry and imbibed cypselas of inbred sunflower (Helianthus annuus L., Asteraceae) lines: B123 (dormant) and B91 (non-dormant). Under our experimental conditions, the expression of RGL2 gene might be related to the ABA peak in B123 line at 3 h of imbibition. Indeed, RGL2 transcripts are absent in dry and early embedded cypselas of the non-dormant line B91. ABA increase was accompanied by a significant ABA-Glucosyl ester (ABA-GE) and phaseic acid (PA) (two ABA catabolites) decrease in B123 line (3 h) which indicates that ABA metabolism seems to be more active in this line, and that it would be involved in the imposition and maintenance of sunflower seed dormancy, as it has been reported for many species. Finally, an increase of bioactive GAs (GA1 and GA3) occurs at 12 h of imbibition in both lines after a decrease in ABA content. This study shows the first report about the RGL2 tissue-specific gene expression in sunflower inbred lines with contrasting dormancy level. Furthermore, our results provide evidence that ABA and GAs content and differential expression of metabolism and signaling genes would be interacting in seed dormancy regulation through a mechanism of action related to embryo itself. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase-epitaxy n-GaAs

NASA Technical Reports Server (NTRS)

Partin, D. L.; Chen, J. W.; Milnes, A. G.; Vassamillet, L. F.

1979-01-01

The paper presents deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase epitaxy n-GaAs. Nickel diffused into VPE n-GaAs reduces the hole diffusion length L sub p from 4.3 to 1.1 microns. Deep-level transient spectroscopy was used to identify energy levels in Ni-diffused GaAs; the as-grown VPE GaAs contains traces of these levels and an electron trap. Ni diffusion reduces the concentration of this level by an amount that matches the increase in concentration of each of the two Ni-related levels. A technique for measuring minority-carrier capture cross sections was developed, which indicates that L sub p in Ni-diffused VPE n-GaAs is controlled by the E sub c - 0.39 eV defect level.

Epistasis Analysis for Estrogen Metabolic and Signaling Pathway Genes on Young Ischemic Stroke Patients

PubMed Central

Hsieh, Yi-Chen; Jeng, Jiann-Shing; Lin, Huey-Juan; Hu, Chaur-Jong; Yu, Chia-Chen; Lien, Li-Ming; Peng, Giia-Sheun; Chen, Chin-I; Tang, Sung-Chun; Chi, Nai-Fang; Tseng, Hung-Pin; Chern, Chang-Ming; Hsieh, Fang-I; Bai, Chyi-Huey; Chen, Yi-Rhu; Chiou, Hung-Yi; Jeng, Jiann-Shing; Tang, Sung-Chun; Yeh, Shin-Joe; Tsai, Li-Kai; Kong, Shin; Lien, Li-Ming; Chiu, Hou-Chang; Chen, Wei-Hung; Bai, Chyi-Huey; Huang, Tzu-Hsuan; Chi-Ieong, Lau; Wu, Ya-Ying; Yuan, Rey-Yue; Hu, Chaur-Jong; Sheu, Jau- Jiuan; Yu, Jia-Ming; Ho, Chun-Sum; Chen, Chin-I; Sung, Jia-Ying; Weng, Hsing-Yu; Han, Yu-Hsuan; Huang, Chun-Ping; Chung, Wen-Ting; Ke, Der-Shin; Lin, Huey-Juan; Chang, Chia-Yu; Yeh, Poh-Shiow; Lin, Kao-Chang; Cheng, Tain-Junn; Chou, Chih-Ho; Yang, Chun-Ming; Peng, Giia-Sheun; Lin, Jiann-Chyun; Hsu, Yaw-Don; Denq, Jong-Chyou; Lee, Jiunn-Tay; Hsu, Chang-Hung; Lin, Chun-Chieh; Yen, Che-Hung; Cheng, Chun-An; Sung, Yueh-Feng; Chen, Yuan-Liang; Lien, Ming-Tung; Chou, Chung-Hsing; Liu, Chia-Chen; Yang, Fu-Chi; Wu, Yi-Chung; Tso, An-Chen; Lai, Yu- Hua; Chiang, Chun-I; Tsai, Chia-Kuang; Liu, Meng-Ta; Lin, Ying-Che; Hsu, Yu-Chuan; Chen, Chih-Hung; Sung, Pi-Shan; Chern, Chang-Ming; Hu, Han-Hwa; Wong, Wen-Jang; Luk, Yun-On; Hsu, Li-Chi; Chung, Chih-Ping; Tseng, Hung-Pin; Liu, Chin-Hsiung; Lin, Chun-Liang; Lin, Hung-Chih; Hu, Chaur-Jong

2012-01-01

Background Endogenous estrogens play an important role in the overall cardiocirculatory system. However, there are no studies exploring the hormone metabolism and signaling pathway genes together on ischemic stroke, including sulfotransferase family 1E (SULT1E1), catechol-O-methyl-transferase (COMT), and estrogen receptor α (ESR1). Methods A case-control study was conducted on 305 young ischemic stroke subjects aged ≦ 50 years and 309 age-matched healthy controls. SULT1E1 -64G/A, COMT Val158Met, ESR1 c.454−397 T/C and c.454−351 A/G genes were genotyped and compared between cases and controls to identify single nucleotide polymorphisms associated with ischemic stroke susceptibility. Gene-gene interaction effects were analyzed using entropy-based multifactor dimensionality reduction (MDR), classification and regression tree (CART), and traditional multiple regression models. Results COMT Val158Met polymorphism showed a significant association with susceptibility of young ischemic stroke among females. There was a two-way interaction between SULT1E1 -64G/A and COMT Val158Met in both MDR and CART analysis. The logistic regression model also showed there was a significant interaction effect between SULT1E1 -64G/A and COMT Val158Met on ischemic stroke of the young (P for interaction = 0.0171). We further found that lower estradiol level could increase the risk of young ischemic stroke for those who carry either SULT1E1 or COMT risk genotypes, showing a significant interaction effect (P for interaction = 0.0174). Conclusions Our findings support that a significant epistasis effect exists among estrogen metabolic and signaling pathway genes and gene-environment interactions on young ischemic stroke subjects. PMID:23112845

Equine fetal adrenal, gonadal and placental steroidogenesis.

PubMed

Legacki, Erin L; Ball, Barry A; Corbin, C Jo; Loux, Shavahn C; Scoggin, Kirsten E; Stanley, Scott D; Conley, Alan J

2017-10-01

Equine fetuses have substantial circulating pregnenolone concentrations and thus have been postulated to provide significant substrate for placental 5α-reduced pregnane production, but the fetal site of pregnenolone synthesis remains unclear. The current studies investigated steroid concentrations in blood, adrenal glands, gonads and placenta from fetuses (4, 6, 9 and 10 months of gestational age (GA)), as well as tissue steroidogenic enzyme transcript levels. Pregnenolone and dehydroepiandrosterone (DHEA) were the most abundant steroids in fetal blood, pregnenolone was consistently higher but decreased progressively with GA. Tissue steroid concentrations generally paralleled those in serum with time. Adrenal and gonadal tissue pregnenolone concentrations were similar and 100-fold higher than those in allantochorion. DHEA was far higher in gonads than adrenals and progesterone was higher in adrenals than gonads. Androstenedione decreased with GA in adrenals but not in gonads. Transcript analysis generally supported these data. CYP17A1 was higher in fetal gonads than adrenals or allantochorion, and HSD3B1 was higher in fetal adrenals and allantochorion than gonads. CYP11A1 transcript was also significantly higher in adrenals and gonads than allantochorion and CYP19 and SRD5A1 transcripts were higher in allantochorion than either fetal adrenals or gonads. Given these data, and their much greater size, the fetal gonads are the source of DHEA and likely contribute more than fetal adrenal glands to circulating fetal pregnenolone concentrations. Low CYP11A1 but high HSD3B1 and SRD5A1 transcript abundance in allantochorion, and low tissue pregnenolone, suggests that endogenous placental pregnenolone synthesis is low and likely contributes little to equine placental 5α-reduced pregnane secretion. © 2017 Society for Reproduction and Fertility.

The rice dwarf virus P2 protein interacts with ent-kaurene oxidases in vivo, leading to reduced biosynthesis of gibberellins and rice dwarf symptoms.

PubMed

Zhu, Shifeng; Gao, Feng; Cao, Xuesong; Chen, Mao; Ye, Gongyin; Wei, Chunhong; Li, Yi

2005-12-01

The mechanisms of viral diseases are a major focus of biology. Despite intensive investigations, how a plant virus interacts with host factors to cause diseases remains poorly understood. The Rice dwarf virus (RDV), a member of the genus Phytoreovirus, causes dwarfed growth phenotypes in infected rice (Oryza sativa) plants. The outer capsid protein P2 is essential during RDV infection of insects and thus influences transmission of RDV by the insect vector. However, its role during RDV infection within the rice host is unknown. By yeast two-hybrid and coimmunoprecipitation assays, we report that P2 of RDV interacts with ent-kaurene oxidases, which play a key role in the biosynthesis of plant growth hormones gibberellins, in infected plants. Furthermore, the expression of ent-kaurene oxidases was reduced in the infected plants. The level of endogenous GA1 (a major active gibberellin in rice vegetative tissues) in the RDV-infected plants was lower than that in healthy plants. Exogenous application of GA3 to RDV-infected rice plants restored the normal growth phenotypes. These results provide evidence that the P2 protein of RDV interferes with the function of a cellular factor, through direct physical interactions, that is important for the biosynthesis of a growth hormone leading to symptom expression. In addition, the interaction between P2 and rice ent-kaurene oxidase-like proteins may decrease phytoalexin biosynthesis and make plants more competent for virus replication. Moreover, P2 may provide a novel tool to investigate the regulation of GA metabolism for plant growth and development.

The Rice Dwarf Virus P2 Protein Interacts with ent-Kaurene Oxidases in Vivo, Leading to Reduced Biosynthesis of Gibberellins and Rice Dwarf Symptoms1

PubMed Central

Zhu, Shifeng; Gao, Feng; Cao, Xuesong; Chen, Mao; Ye, Gongyin; Wei, Chunhong; Li, Yi

2005-01-01

The mechanisms of viral diseases are a major focus of biology. Despite intensive investigations, how a plant virus interacts with host factors to cause diseases remains poorly understood. The Rice dwarf virus (RDV), a member of the genus Phytoreovirus, causes dwarfed growth phenotypes in infected rice (Oryza sativa) plants. The outer capsid protein P2 is essential during RDV infection of insects and thus influences transmission of RDV by the insect vector. However, its role during RDV infection within the rice host is unknown. By yeast two-hybrid and coimmunoprecipitation assays, we report that P2 of RDV interacts with ent-kaurene oxidases, which play a key role in the biosynthesis of plant growth hormones gibberellins, in infected plants. Furthermore, the expression of ent-kaurene oxidases was reduced in the infected plants. The level of endogenous GA1 (a major active gibberellin in rice vegetative tissues) in the RDV-infected plants was lower than that in healthy plants. Exogenous application of GA3 to RDV-infected rice plants restored the normal growth phenotypes. These results provide evidence that the P2 protein of RDV interferes with the function of a cellular factor, through direct physical interactions, that is important for the biosynthesis of a growth hormone leading to symptom expression. In addition, the interaction between P2 and rice ent-kaurene oxidase-like proteins may decrease phytoalexin biosynthesis and make plants more competent for virus replication. Moreover, P2 may provide a novel tool to investigate the regulation of GA metabolism for plant growth and development. PMID:16299167

Endogenous benzodiazepine-like compounds and diazepam binding inhibitor in serum of patients with liver cirrhosis with and without overt encephalopathy

PubMed Central

Avallone, R; Zeneroli, M; Venturini, I; Corsi, L; Schreier, P; Kleinschnitz, M; Ferrarese, C; Farina, F; Baraldi, C; Pecora, N; Frigo, M; Baraldi, M

1998-01-01

Background/Aim—Despite some controversy, it has been suggested that endogenous benzodiazepine plays a role in the pathogenesis of hepatic encephalopathy. The aim of the present study was to evaluate the concentrations of endogenous benzodiazepines and the peptide, diazepam binding inhibitor, in the blood of patients with liver cirrhosis with and without overt encephalopathy, and to compare these levels with those of consumers of commercial benzodiazepines. 
Subjects—Normal subjects (90), benzodiazepine consumers (14), and cirrhotic patients (113) were studied. 
Methods—Endogenous benzodiazepines were measured by the radioligand binding technique after high performance liquid chromatography (HPLC) purification. The presence of diazepam and N-desmethyldiazepam was assayed by HPLC-electrospray tandem mass spectrometry. Diazepam binding inhibitor was studied in serum by radioimmunoassay. 
Results—Endogenous benzodiazepines were below the limit of detection in 7% of patients with encephalopathy. When detectable, their levels were at least comparable with those of benzodiazepine consumers and correlated with the liver dysfunction but not the stage of encephalopathy. Serum levels of diazepam binding inhibitor tended to decrease when endogenous benzodiazepines levels increased. 
Conclusions—Endogenous benzodiazepines may accumulate in patients with liver cirrhosis during the course of the disease, and the phenomenon appears to be independent of the presence or absence of encephalopathy. 

 Keywords: benzodiazepine consumers; diazepam binding inhibitor; endogenous benzodiazepines; liver cirrhosis; overt hepatic encephalopathy PMID:9691927

Repeated immobilization stress alters rat hippocampal and prefrontal cortical morphology in parallel with endogenous agmatine and arginine decarboxylase levels

PubMed Central

Zhu, Meng-Yang; Wang, Wei-Ping; Huang, Jingjing; Feng, Yang-Zheng; Regunathan, Soundar; Bissette, Garth

2008-01-01

Agmatine, an endogenous amine derived from decarboxylation of L-arginine catalyzed by arginine decarboxylase, has been proposed as a neurotransmitter or neuromodulator in the brain. In the present study we examined whether agmatine has neuroprotective effects against repeated immobilization-induced morphological changes in brain tissues and possible effects of immobilization stress on endogenous agmatine levels and arginine decarboxylase expression in rat brains. Sprague-Dawley rats were subjected to two hour immobilization stress daily for seven days. This paradigm significantly increased plasma corticosterone levels, and the glutamate efflux in the hippocampus as measured by in vivo microdialysis. Immunohistochemical staining with β-tubulin III showed that repeated immobilization caused marked morphological alterations in the hippocampus and medial prefrontal cortex that were prevented by simultaneous treatment with agmatine (50 mg/kg/day, i.p.). Likewise, endogenous agmatine levels measured by high performance liquid chromatography in the prefrontal cortex, hippocampus, striatum and hypothalamus were significantly increased by immobilization, as compared to controls. The increased endogenous agmatine levels, ranging from 92% to 265% of controls, were accompanied by a significant increase of arginine decarboxylase protein levels in the same regions. These results demonstrate that administration of exogenous agmatine protects the hippocampus and medial prefrontal cortex against neuronal insults caused by repeated immobilization. The parallel increase in endogenous brain agmatine and arginine decarboxylase protein levels triggered by repeated immobilization indicates that the endogenous agmatine system may play an important role in adaptation to stress as a potential neuronal self-protection mechanism. PMID:18832001

Soluble thrombomodulin levels in plasma of multiple sclerosis patients and their implication.

PubMed

Festoff, Barry W; Li, Chaoyang; Woodhams, Barry; Lynch, Sharon

2012-12-15

Thrombomodulin (TM) on the cell-surface of cerebrovascular endothelial cells (CECs) is released into blood upon CEC damage. TM promotes activation of protein C (APC), an anticoagulant, anti-inflammatory, neuroprotective molecule that protects CECs and impedes inflammatory cell migration across the blood-brain barrier (BBB). Multiple sclerosis (MS) is associated with CEC damage and BBB dysfunction. We evaluated soluble TM (sTM) levels as a biomarker of BBB integrity and whether glatiramer acetate (GA) influenced sTM levels in MS patients. sTM levels quantified by 2-site ELISA from sera of healthy controls and systemic lupus erythematosus (SLE) patients (CEC-damage positive control) were compared with levels from patients with relapsing-remitting (RRMS) or secondary-progressive MS (SPMS), stratified as: RRMS/GA/no relapse, RRMS/GA/in relapse, RRMS no GA/no relapse, RRMS/no GA/in relapse; and SPMS/no GA. Additionally, soluble endothelial protein C receptor (sEPCR) levels were assessed in the non-stratified MS group, SLE patients, and controls. sTM levels were highest in RRMS patients taking GA with or without relapse, followed in decreasing order by SLE, RRMS/no GA/in relapse, SPMS, RRMS/no GA/no relapse, healthy controls. sEPCR levels were highest in MS patients, then SLE, then controls. sTM may be a useful biomarker of BBB integrity in RRMS patients. Further evaluation of sEPCR is needed. The finding that the highest sTM levels were in RRMS patients taking GA is interesting and warrants further investigation. Published by Elsevier B.V.

Contactless electroreflectance study of the Fermi level pinning on GaSb surface in n-type and p-type GaSb Van Hoof structures

NASA Astrophysics Data System (ADS)

Kudrawiec, R.; Nair, H. P.; Latkowska, M.; Misiewicz, J.; Bank, S. R.; Walukiewicz, W.

2012-12-01

Contactless electroreflectance (CER) has been applied to study the Fermi-level position on GaSb surface in n-type and p-type GaSb Van Hoof structures. CER resonances, followed by strong Franz-Keldysh oscillation of various periods, were clearly observed for two series of structures. This period was much wider (i.e., the built-in electric field was much larger) for n-type structures, indicating that the GaSb surface Fermi level pinning position is closer to the valence-band than the conduction-band. From analysis of the built-in electric fields in undoped GaSb layers, it was concluded that on GaSb surface the Fermi-level is located ˜0.2 eV above the valence band.

Evolution of AlGaN deep level defects as a function of alloying and compositional grading and resultant impact on electrical conductivity

DOE PAGES

Armstrong, Andrew M.; Allerman, Andrew A.

2017-07-24

AlGaN:Si epilayers with uniform Al compositions of 60%, 70%, 80%, and 90% were grown by metal-organic vapor phase epitaxy along with a compositionally graded, unintentionally doped (UID) AlGaN epilayer with the Al composition varying linearly between 80% and 100%. The resistivity of AlGaN:Si with a uniform composition increased significantly for the Al content of 80% and greater, whereas the graded UID-AlGaN film exhibited resistivity equivalent to 60% and 70% AlGaN:Si owing to polarization-induced doping. Deep level defect studies of both types of AlGaN epilayers were performed to determine why the electronic properties of uniform-composition AlGaN:Si degraded with increased Al content,more » while the electronic properties of graded UID-AlGaN did not. The deep level density of uniform-composition AlGaN:Si increased monotonically and significantly with the Al mole fraction. Conversely, graded-UID AlGaN had the lowest deep level density of all the epilayers despite containing the highest Al composition. These findings indicate that Si doping is an impetus for point defect incorporation in AlGaN that becomes stronger with the increasing Al content. However, the increase in deep level density with the Al content in uniform-composition AlGaN:Si was small compared to the increase in resistivity. This implies that the primary cause for increasing resistivity in AlGaN:Si with the increasing Al mole fraction is not compensation by deep levels but rather increasing activation energy for the Si dopant. As a result, the graded UID-AlGaN films maintained low resistivity because they do not rely on thermal ionization of Si dopants.« less

Evolution of AlGaN deep level defects as a function of alloying and compositional grading and resultant impact on electrical conductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armstrong, Andrew M.; Allerman, Andrew A.

AlGaN:Si epilayers with uniform Al compositions of 60%, 70%, 80%, and 90% were grown by metal-organic vapor phase epitaxy along with a compositionally graded, unintentionally doped (UID) AlGaN epilayer with the Al composition varying linearly between 80% and 100%. The resistivity of AlGaN:Si with a uniform composition increased significantly for the Al content of 80% and greater, whereas the graded UID-AlGaN film exhibited resistivity equivalent to 60% and 70% AlGaN:Si owing to polarization-induced doping. Deep level defect studies of both types of AlGaN epilayers were performed to determine why the electronic properties of uniform-composition AlGaN:Si degraded with increased Al content,more » while the electronic properties of graded UID-AlGaN did not. The deep level density of uniform-composition AlGaN:Si increased monotonically and significantly with the Al mole fraction. Conversely, graded-UID AlGaN had the lowest deep level density of all the epilayers despite containing the highest Al composition. These findings indicate that Si doping is an impetus for point defect incorporation in AlGaN that becomes stronger with the increasing Al content. However, the increase in deep level density with the Al content in uniform-composition AlGaN:Si was small compared to the increase in resistivity. This implies that the primary cause for increasing resistivity in AlGaN:Si with the increasing Al mole fraction is not compensation by deep levels but rather increasing activation energy for the Si dopant. As a result, the graded UID-AlGaN films maintained low resistivity because they do not rely on thermal ionization of Si dopants.« less

Defects and annealing studies in 1-Me electron irradiated (AlGa)As-GaAs solar cells

NASA Technical Reports Server (NTRS)

Li, S. S.; Wang, W. L.; Loo, R. Y.; Rahilly, W. P.

1982-01-01

The deep-level defects and recombination mechanisms in the one-MeV electron irradiated (AlGa)As-GaAs solar cells under various irradiation and annealing conditions are discussed. Deep-level transient spectroscopy (DLTS) and capacitance-voltage (CV) techniques were used to determine the defect and recombination parameters such as energy levels and defect density, carrier capture cross sections and lifetimes for both electron and hole traps as well as hole diffusion lengths in these electron irradiated GaAs solar cells. GaAs solar cells used in this study were prepared by the infinite solution melt liquid phase epitaxial (LPE) technique at Hughes Research Lab., with (Al0.9Ga0.1)-As window layer, Be-diffused p-GaAs layer on Sn-doped n-GaAs or undoped n-GaAs active layer grown on n(+)-GaAs substrate. Mesa structure with area of 5.86x1000 sq cm was fabricated. Three different irradiation and annealing experiments were performed on these solar cells.

Balance between salt stress and endogenous hormones influence dry matter accumulation in Jerusalem artichoke.

PubMed

Shao, Tianyun; Li, Lingling; Wu, Yawen; Chen, Manxia; Long, Xiaohua; Shao, Hongbo; Liu, Zhaopu; Rengel, Zed

2016-10-15

Salinity is one of the most serious environmental stresses limiting agricultural production. Production of Jerusalem artichoke on saline land is strategically important for using saline land resources. The interaction between plant hormones and salinity stress in governing Jerusalem artichoke (Helianthus tuberosus) growth is unclear. Jerusalem artichoke (variety Nanyu-1) was grown under variable salinity stress in the field, and a role of endogenous hormones [zeatin (ZT), auxins (IAA), gibberellins (GA3) and abscisic acid (ABA)] in regulating sugar and dry matter accumulation in tubers was characterized. Under mild salt stress (≤2.2gNaClkg(-1) soil), Nanyu-1 grew well with no significant alteration of dry matter distribution to stems and tubers. In contrast, under moderate salt stress (2.7gNaClkg(-1) soil), the distribution to stem decreased and to tubers decreased significantly. Mild salt stress induced sugar accumulation in tubers at the beginning of the tuber-expansion period, but significantly inhibited (i) transfer of non-reducing sugars to tubers, and (ii) polymerization and accumulation of fructan during the tuber-expansion stage. Under different salinity stress, before the stolon growth, the ratio of IAA/ABA in leaves increased significantly and that of GA3/ABA increased slightly; during tuber development, these ratios continued to decrease and reached the minimum late in the tuber-expansion period. While, salt stress inhibited (i) underground dry matter accumulation, (ii) tuber dry matter accumulation efficiency, (iii) transport of non-reducing sugars to tubers, and (iv) fructan accumulation efficiency during the tuber-expansion period; these effects were accompanied by significantly decreased tuber yield with an increase in salinity. With soil salinity increasing, the synthesis of IAA and GA3 was inhibited in leaves and tubers, while ABA synthesis was stimulated. In brief, tuber yield would significantly decreased with the increase of salinity. Copyright © 2016 Elsevier B.V. All rights reserved.

Release of the repressive activity of rice DELLA protein SLR1 by gibberellin does not require SLR1 degradation in the gid2 mutant.

PubMed

Ueguchi-Tanaka, Miyako; Hirano, Ko; Hasegawa, Yasuko; Kitano, Hidemi; Matsuoka, Makoto

2008-09-01

The rice (Oryza sativa) DELLA protein SLR1 acts as a repressor of gibberellin (GA) signaling. GA perception by GID1 causes SLR1 protein degradation involving the F-box protein GID2; this triggers GA-associated responses such as shoot elongation and seed germination. In GA-insensitive and GA biosynthesis mutants, SLENDER RICE1 (SLR1) accumulates to high levels, and the severity of dwarfism is usually correlated with the level of SLR1 accumulation. An exception is the GA-insensitive F-box mutant gid2, which shows milder dwarfism than mutants such as gid1 and cps even though it accumulates higher levels of SLR1. The level of SLR1 protein in gid2 was decreased by loss of GID1 function or treatment with a GA biosynthesis inhibitor, and dwarfism was enhanced. Conversely, overproduction of GID1 or treatment with GA(3) increased the SLR1 level in gid2 and reduced dwarfism. These results indicate that derepression of SLR1 repressive activity can be accomplished by GA and GID1 alone and does not require F-box (GID2) function. Evidence for GA signaling without GID2 was also provided by the expression behavior of GA-regulated genes such as GA-20oxidase1, GID1, and SLR1 in the gid2 mutant. Based on these observations, we propose a model for the release of GA suppression that does not require DELLA protein degradation.

Brassinosteroid Regulates Cell Elongation by Modulating Gibberellin Metabolism in Rice[C][W][OPEN

PubMed Central

Tong, Hongning; Xiao, Yunhua; Liu, Dapu; Gao, Shaopei; Liu, Linchuan; Yin, Yanhai; Jin, Yun; Qian, Qian; Chu, Chengcai

2014-01-01

Brassinosteroid (BR) and gibberellin (GA) are two predominant hormones regulating plant cell elongation. A defect in either of these leads to reduced plant growth and dwarfism. However, their relationship remains unknown in rice (Oryza sativa). Here, we demonstrated that BR regulates cell elongation by modulating GA metabolism in rice. Under physiological conditions, BR promotes GA accumulation by regulating the expression of GA metabolic genes to stimulate cell elongation. BR greatly induces the expression of D18/GA3ox-2, one of the GA biosynthetic genes, leading to increased GA1 levels, the bioactive GA in rice seedlings. Consequently, both d18 and loss-of-function GA-signaling mutants have decreased BR sensitivity. When excessive active BR is applied, the hormone mostly induces GA inactivation through upregulation of the GA inactivation gene GA2ox-3 and also represses BR biosynthesis, resulting in decreased hormone levels and growth inhibition. As a feedback mechanism, GA extensively inhibits BR biosynthesis and the BR response. GA treatment decreases the enlarged leaf angles in plants with enhanced BR biosynthesis or signaling. Our results revealed a previously unknown mechanism underlying BR and GA crosstalk depending on tissues and hormone levels, which greatly advances our understanding of hormone actions in crop plants and appears much different from that in Arabidopsis thaliana. PMID:25371548

Phenylpropanoid 2,3-dioxygenase involved in the cleavage of the ferulic acid side chain to form vanillin and glyoxylic acid in Vanilla planifolia.

PubMed

Negishi, Osamu; Negishi, Yukiko

2017-09-01

Enzyme catalyzing the cleavage of the phenylpropanoid side chain was partially purified by ion exchange and gel filtration column chromatography after (NH 4 ) 2 SO 4 precipitation. Enzyme activities were dependent on the concentration of dithiothreitol (DTT) or glutathione (GSH) and activated by addition of 0.5 mM Fe 2+ . Enzyme activity for ferulic acid was as high as for 4-coumaric acid in the presence of GSH, suggesting that GSH acts as an endogenous reductant in vanillin biosynthesis. Analyses of the enzymatic reaction products with quantitative NMR (qNMR) indicated that an amount of glyoxylic acid (GA) proportional to vanillin was released from ferulic acid by the enzymatic reaction. These results suggest that phenylpropanoid 2,3-dioxygenase is involved in the cleavage of the ferulic acid side chain to form vanillin and GA in Vanilla planifolia.

Serum cystatin C levels in preterm newborns in our setting: Correlation with serum creatinine and preterm pathologies.

PubMed

Bardallo Cruzado, Leonor; Pérez González, Elena; Martínez Martos, Zoraima; Bermudo Guitarte, Carmen; Granero Asencio, Mercedes; Luna Lagares, Salud; Marín Patón, Mariano; Polo Padilla, Juan

2015-01-01

Cystatin C (CysC) is a renal function marker that is not as influenced as creatinine (Cr) by endogenous or exogenous agents, so it is therefore proposed as a marker in preterm infants. To determine serum CysC values in preterm infants during the first week of life, compared to Cr. To analyze alterations caused by prematurity diseases. The design involved a longitudinal, observational study of prospective cohorts. Groups were based on gestational age (GA): Group A (24-27 weeks), Group B (28-33 weeks), Group C (34-36 weeks). Blood samples were collected at birth, within 48-72hours and after 7 days of life. SPSS v.20 software was used. The statistical methods applied included chi-squared test and ANOVA. A total of 109 preterm infants were included in the study. CysC levels were: 1.54mg/L (±0.28) at birth; 1.38mg/L (±0.36) within 48-72hours of life; 1.50mg/L (±0.31) after 7 days (p<0.05). Cr levels were: 0.64mg/dL (±0.17) at birth; 0.64mg/dL (±0.28) within 48-72hours; 0.56mg/dL (±0.19) after 7 days (P<.05). CysC values were lower in hypotensive patients and those with a respiratory disease (P<.05), and no alterations associated with other diseases were observed. There were no differences in Cr levels associated with any disease. Creatinine levels were higher in patients ≤1.500g (P<.05). Serum CysC decreased within 48-72hours of life, and this decline showed significance (P<.05). The levels increased after 7 days in all 3 GA groups, and there was no difference in CysC levels among the groups. More studies in preterm infants with hypotension and respiratory disease are required. CysC is a better glomerular filtration (GF) marker in ≤1.500g preterm infants. Copyright © 2015 The Authors. Published by Elsevier España, S.L.U. All rights reserved.

Molecular cloning and photoperiod-regulated expression of gibberellin 20-oxidase from the long-day plant spinach.

PubMed

Wu, K; Li, L; Gage, D A; Zeevaart, J A

1996-02-01

Spinach (Spinacia oleracea L.) is a long-day (LD) rosette plant in which stem growth under LD conditions is mediated by gibberellins (GAs). Major control points in spinach are the later steps of sequential oxidation and elimination of C-20 of C20-GAs. Degenerate oligonucleotide primers were used to obtain a polymerase chain reaction product from spinach genomic DNA that has a high homology with GA 20-oxidase cDNAs from Cucurbita maxima L. and Arabidopsis thaliana Heynh. This polymerase chain reaction product was used as a probe to isolate a full-length cDNA clone with an open reading frame encoding a putative 43-kD protein of 374 amino acid residues. When this cDNA clone was expressed in Escherichia coli, the fusion protein catalyzed the biosynthetic sequence GA53-->GA44-->GA19-->GA20 and GA19-->GA17. This establishes that in spinach a single protein catalyzes the oxidation and elimination of C-20. Transfer of spinach plants from short day (SD) to LD conditions caused an increase in the level of all GAs of the early-13-hydroxylation pathway, except GA53, with GA20, GA1, and GA8 showing the largest increases. Northern blot analysis indicated that the level of GA 20-oxidase mRNA was higher in plants in LD than in SD conditions, with highest level of expression in the shoot tips and elongating stems. This expression pattern of GA 20-oxidase is consistent with the different levels of GA20, GA1, and GA8 found in spinach plants grown in SD and LD conditions.

The thickness design of unintentionally doped GaN interlayer matched with background doping level for InGaN-based laser diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, P.; Zhao, D. G., E-mail: dgzhao@red.semi.ac.cn; Jiang, D. S.

2016-03-15

In order to reduce the internal optical loss of InGaN laser diodes, an unintentionally doped GaN (u-GaN) interlayer is inserted between InGaN/GaN multiple quantum well active region and Al{sub 0.2}Ga{sub 0.8}N electron blocking layer. The thickness design of u-GaN interlayer matching up with background doping level for improving laser performance is studied. It is found that a suitably chosen u-GaN interlayer can well modulate the optical absorption loss and optical confinement factor. However, if the value of background doping concentration of u-GaN interlayer is too large, the output light power may decrease. The analysis of energy band diagram of amore » LD structure with 100 nm u-GaN interlayer shows that the width of n-side depletion region decreases when the background concentration increases, and may become even too small to cover whole MQW, resulting in a serious decrease of the output light power. It means that a suitable interlayer thickness design matching with the background doping level of u-GaN interlayer is significant for InGaN-based laser diodes.« less

GaAs VLSI technology and circuit elements for DSP

NASA Astrophysics Data System (ADS)

Mikkelson, James M.

1990-10-01

Recent progress in digital GaAs circuit performance and complexity is presented to demonstrate the current capabilities of GaAs components. High density GaAs process technology and circuit design techniques are described and critical issues for achieving favorable complexity speed power and cost tradeoffs are reviewed. Some DSP building blocks are described to provide examples of what types of DSP systems could be implemented with present GaAs technology. DIGITAL GaAs CIRCUIT CAPABILITIES In the past few years the capabilities of digital GaAs circuits have dramatically increased to the VLSI level. Major gains in circuit complexity and power-delay products have been achieved by the use of silicon-like process technologies and simple circuit topologies. The very high speed and low power consumption of digital GaAs VLSI circuits have made GaAs a desirable alternative to high performance silicon in hardware intensive high speed system applications. An example of the performance and integration complexity available with GaAs VLSI circuits is the 64x64 crosspoint switch shown in figure 1. This switch which is the most complex GaAs circuit currently available is designed on a 30 gate GaAs gate array. It operates at 200 MHz and dissipates only 8 watts of power. The reasons for increasing the level of integration of GaAs circuits are similar to the reasons for the continued increase of silicon circuit complexity. The market factors driving GaAs VLSI are system design methodology system cost power and reliability. System designers are hesitant or unwilling to go backwards to previous design techniques and lower levels of integration. A more highly integrated system in a lower performance technology can often approach the performance of a system in a higher performance technology at a lower level of integration. Higher levels of integration also lower the system component count which reduces the system cost size and power consumption while improving the system reliability. For large gate count circuits the power per gate must be minimized to prevent reliability and cooling problems. The technical factors which favor increasing GaAs circuit complexity are primarily related to reducing the speed and power penalties incurred when crossing chip boundaries. Because the internal GaAs chip logic levels are not compatible with standard silicon I/O levels input receivers and output drivers are needed to convert levels. These I/O circuits add significant delay to logic paths consume large amounts of power and use an appreciable portion of the die area. The effects of these I/O penalties can be reduced by increasing the ratio of core logic to I/O on a chip. DSP operations which have a large number of logic stages between the input and the output are ideal candidates to take advantage of the performance of GaAs digital circuits. Figure 2 is a schematic representation of the I/O penalties encountered when converting from ECL levels to GaAs

Brassinosteroid regulates cell elongation by modulating gibberellin metabolism in rice.

PubMed

Tong, Hongning; Xiao, Yunhua; Liu, Dapu; Gao, Shaopei; Liu, Linchuan; Yin, Yanhai; Jin, Yun; Qian, Qian; Chu, Chengcai

2014-11-01

Brassinosteroid (BR) and gibberellin (GA) are two predominant hormones regulating plant cell elongation. A defect in either of these leads to reduced plant growth and dwarfism. However, their relationship remains unknown in rice (Oryza sativa). Here, we demonstrated that BR regulates cell elongation by modulating GA metabolism in rice. Under physiological conditions, BR promotes GA accumulation by regulating the expression of GA metabolic genes to stimulate cell elongation. BR greatly induces the expression of D18/GA3ox-2, one of the GA biosynthetic genes, leading to increased GA1 levels, the bioactive GA in rice seedlings. Consequently, both d18 and loss-of-function GA-signaling mutants have decreased BR sensitivity. When excessive active BR is applied, the hormone mostly induces GA inactivation through upregulation of the GA inactivation gene GA2ox-3 and also represses BR biosynthesis, resulting in decreased hormone levels and growth inhibition. As a feedback mechanism, GA extensively inhibits BR biosynthesis and the BR response. GA treatment decreases the enlarged leaf angles in plants with enhanced BR biosynthesis or signaling. Our results revealed a previously unknown mechanism underlying BR and GA crosstalk depending on tissues and hormone levels, which greatly advances our understanding of hormone actions in crop plants and appears much different from that in Arabidopsis thaliana. © 2014 American Society of Plant Biologists. All rights reserved.

The unsolved puzzle of neuropathogenesis in glutaric aciduria type I.

PubMed

Jafari, Paris; Braissant, Olivier; Bonafé, Luisa; Ballhausen, Diana

2011-12-01

Glutaric aciduria type I (GA-I) is a cerebral organic aciduria caused by deficiency of glutaryl-Co-A dehydrogenase (GCDH). GCDH deficiency leads to accumulation of glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA), two metabolites that are believed to be neurotoxic, in brain and body fluids. The disorder usually becomes clinically manifest during a catabolic state (e.g. intercurrent illness) with an acute encephalopathic crisis that results in striatal necrosis and in a permanent dystonic-dyskinetic movement disorder. The results of numerous in vitro and in vivo studies have pointed to three main mechanisms involved in the metabolite-mediated neuronal damage: excitotoxicity, impairment of energy metabolism and oxidative stress. There is evidence that during a metabolic crisis GA and its metabolites are produced endogenously in the CNS and accumulate because of limiting transport mechanisms across the blood-brain barrier. Despite extensive experimental work, the relative contribution of the proposed pathogenic mechanisms remains unclear and specific therapeutic approaches have yet to be developed. Here, we review the experimental evidence and try to delineate possible pathogenetic models and approaches for future studies. Copyright © 2011 Elsevier Inc. All rights reserved.

Opposing effects of external gibberellin and Daminozide on Stevia growth and metabolites.

PubMed

Karimi, Mojtaba; Hashemi, Javad; Ahmadi, Ali; Abbasi, Alireza; Pompeiano, Antonio; Tavarini, Silvia; Guglielminetti, Lorenzo; Angelini, Luciana G

2015-01-01

Steviol glycosides (SVglys) and gibberellins are originated from the shared biosynthesis pathway in Stevia (Stevia rebaudiana Bertoni). In this research, two experiments were conducted to study the opposing effects of external gibberellin (GA3) and Daminozide (a gibberellin inhibitor) on Stevia growth and metabolites. Results showed that GA3 significantly increased the stem length and stem dry weight in Stevia. Total soluble sugar content increased while the SVglys biosynthesis was decreased by external GA3 applying in Stevia leaves. In another experiment, the stem length was reduced by Daminozide spraying on Stevia shoots. The Daminozide did not affect the total SVglys content, while in 30 ppm concentration, significantly increased the soluble sugar production in Stevia leaves. Although the gibberellins biosynthesis pathway has previously invigorated in Stevia leaf, the Stevia response to external gibberellins implying on high precision regulation of gibberellins biosynthesis in Stevia and announces that Stevia is able to kept endogenous gibberellins in a low quantity away from SVglys production. Moreover, the assumption that the internal gibberellins were destroyed by Daminozide, lack of Daminozide effects on SVglys production suggests that gibberellins biosynthesis could not act as a competitive factor for SVglys production in Stevia leaves.

On the validity of the amphoteric-defect model in gallium arsenide and a criterion for Fermi-level pinning by defects

NASA Astrophysics Data System (ADS)

Chen, C.-H.; Tan, T. Y.

1995-10-01

Using the theoretically calculated point-defect total-energy values of Baraff and Schlüter in GaAs, an amphoteric-defect model has been proposed by Walukiewicz to explain a large number of experimental results. The suggested amphoteric-defect system consists of two point-defect species capable of transforming into each other: the doubly negatively charged Ga vacancy V {Ga/2-} and the triply positively charged defect complex (ASGa+ V As)3+, with AsGa being the antisite defect of an As atom occupying a Ga site and V As being an As vacancy. When present in sufficiently high concentrations, the amphoteric defect system V {Ga/2-}/(AsGa+ V As)3+ is supposed to be able to pin the GaAs Fermi level at approximately the E v +0.6 eV level position, which requires that the net free energy of the V Ga/(AsGa+ V As) defect system to be minimum at the same Fermi-level position. We have carried out a quantitative study of the net energy of this defect system in accordance with the individual point-defect total-energy results of Baraff and Schlüter, and found that the minimum net defect-system-energy position is located at about the E v +1.2 eV level position instead of the needed E v +0.6 eV position. Therefore, the validity of the amphoteric-defect model is in doubt. We have proposed a simple criterion for determining the Fermi-level pinning position in the deeper part of the GaAs band gap due to two oppositely charged point-defect species, which should be useful in the future.

Effect of storage temperature on endogenous GHB levels in urine.

PubMed

LeBeau, M A; Miller, M L; Levine, B

2001-06-15

Because gamma-hydroxybutyrate (GHB) is an endogenous substance present in the body and is rapidly eliminated after ingestion, toxicologists investigating drug-facilitated sexual assault cases are often asked to differentiate between endogenous and exogenous levels of GHB in urine samples. This study was designed to determine the effects of storage temperature on endogenous GHB levels in urine. Specifically, it was designed to ascertain whether endogenous levels can be elevated to a range considered indicative of GHB ingestion. Urine specimens from two subjects that had not been administered exogenous GHB were collected during a 24h period and individually pooled. The pooled specimens were separated into standard sample cups and divided into three storage groups: room temperature ( approximately 25 degrees C), refrigerated (5 degrees C), and frozen (-10 degrees C). Additionally, some specimens were put through numerous freeze/thaw cycles to mimic situations that may occur if multiple laboratories analyze the same specimen. Periodic analysis of the samples revealed increases in the levels of endogenous GHB over a 6-month period. The greatest increase (up to 404%) was observed in the samples maintained at room temperature. The refrigerated specimens showed increases of 140-208%, while the frozen specimens showed smaller changes (88-116%). The specimens subjected to multiple freeze/thaw cycles mirrored specimens that had been thawed only once. None of the stored urine specimens demonstrated increases in GHB concentrations that would be consistent with exogenous GHB ingestion.

High Dielectrics on High Carrier Mobility InGaAs Compound Semiconductors and GaN - Growth, Interfacial Structural Studies, and Surface Fermi Level Unpinning

DTIC Science & Technology

2010-02-19

UHV- deposited Al2O3(3nm)/ Ga2O3 (Gd2O3)(8.5nm) on n- and p-In0.2Ga0.8As/GaAs. The results exhibit very high-quality interface and free-moving Fermi...κ Ga2O3 (Gd2O3) [GGO] and Gd2O3 on InGaAs, without an interfacial layer. InxGa1−xAs MOSFETs have been successfully demonstrated with excellent device... Ga2O3 (Gd2O3)/In0.2Ga0.8As and high temperature (850°C) stability Scaling high κ oxides to nanometer range as well as unpinning surface Fermi level

Predictions of ground states of LiGa and NaGa

NASA Astrophysics Data System (ADS)

Boldyrev, Alexander I.; Simons, Jack

1996-11-01

The ground and very low-lying excited states of LiGa and NaGa have been studied using high level ab initio techniques. At the QCISD(T)/6-311 + G(2df) level of theory, the 1Σ + state was found to be the most stable for both molecules. The equilibrium bond lengths and dissociation energies were found to be: R( LiGa) = 2.865 Å and D0(LiGa) = 22.3 kcal/mol and R( NaGa) = 3.174 Å and D0(NaGa) = 17.1 kcal/mol. Trends within the ground electronic states of LiB, NaB, LiAl, NaAl, LiGa and NaGa are discussed and predictions for related AlkM (Alk LiCs and MBTl) species are made.

Regulation and physiological role of silicon in alleviating drought stress of mango.

PubMed

Helaly, Mohamed Naser; El-Hoseiny, Hanan; El-Sheery, Nabil Ibrahim; Rastogi, Anshu; Kalaji, Hazem M

2017-09-01

Improvement of drought stress of mango plants requires intensive research that focuses on physiological processes. In three successive seasons (2014, 2015and 2016) field experiments with four different strains of mango were subjected to two water regimes. The growth and physiological parameters of possible relevance for drought stress tolerances in mango were investigated. Yield and its components were also evaluated. The data showed that all growth and physiological parameters were increased under K 2 SiO 3 (Si) supplement and were followed by the interaction treatment (Si treatment and its combination with drought stress) compared to that of the controlled condition. Drought stress decreased the concentration of auxins (IAA), gibberellins (GA) and cytokinins (CK) in the three mango cultivars leaves, whereas, it increased the concentration of abscisic acid (ABA). On the contrary, IAA, GA, and CK (promoters) endogenous levels were improved by supplementing Si, in contrary ABA was decreased. Drought stress increased the activity of peroxidase (POX), catalase (CAT), and superoxide dismutase (SOD) in the leaves of all mango cultivars grown during three experimental seasons. However, Si supplementation reduced the levels of all these antioxidative enzymes, especially the concentration of SOD when compared to that of control leaves. Fruit quality was improved in three successive seasons when Si was applied. Our results clearly show that the increment in drought tolerance was associated with an increase in antioxidative enzyme activity, allowing mango plants to cope better with drought stress. Si possesses an efficient system for scavenging reactive oxygen species, which protects the plant against destructive oxidative reactions, thereby improving the ability of the mango trees to withstand environmental stress in arid regions. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Coagulation indices in very preterm infants from cord blood and postnatal samples.

PubMed

Neary, E; McCallion, N; Kevane, B; Cotter, M; Egan, K; Regan, I; Kirkham, C; Mooney, C; Coulter-Smith, S; Ní Áinle, F

2015-11-01

Very premature infants are at high risk of bleeding complications; however, few data exist on ranges for standard coagulation tests. The primary objective of this study was to measure standard plasma coagulation tests and thrombin generation in very premature infants compared with term infants. The secondary objective was to evaluate whether an association existed between coagulation indices and intraventricular hemorrhage (IVH). Cord and peripheral blood of neonates < 30 weeks gestational age (GA) was drawn at birth, on days 1 and 3 and fortnightly until 30 weeks corrected gestational age. Prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen and coagulation factor levels were measured and tissue factor-stimulated thrombin generation was characterized. Control plasma was obtained from cord blood of term neonates. One hundred and sixteen infants were recruited. Median (range) GA was 27.7 (23.7-29.9) weeks and mean (SD) birth weight was 1020 (255) g. Median (5th-95th percentile) day 1 PT, APTT and fibrinogen were 17.5 (12.7-26.6) s, 78.7 (48.7-134.3) s and 1.4 (0.72-3.8) g L(-1) , respectively. No difference in endogenous thrombin potential between preterm and term plasma was observed, where samples were available. Levels of coagulation factors II, VII, IX and X, protein C, protein S and antithrombin were reduced in preterm compared with term plasma. Day 1 APTT and PT were not associated with IVH. In the largest cross-sectional study to date of very preterm infants, typical ranges for standard coagulation tests were determined. Despite long clotting times, thrombin generation was observed to be similar in very preterm and term infants. © 2015 International Society on Thrombosis and Haemostasis.

U-Pb SHRIMP II age and origin of zircon from lhertzolite of the bug Paleoarchean complex, Ukrainian Shield

NASA Astrophysics Data System (ADS)

Lobach-Zhuchenko, S. B.; Baltybaev, Sh. K.; Glebovitsky, V. A.; Sergeev, S. A.; Lokhov, K. O.; Egorova, Yu. S.; Balagansky, V. V.; Skublov, S. G.; Galankina, O. L.; Stepanyuk, L. M.

2017-12-01

Complex study of the U-Pb and Lu-Hf systems of zircon from a lhertzolite lens of Archean gneiss enderbites of the Bug complex, Ukrainian Shield, showed that ultramafic magma was contaminated by the material of the country gneiss enderbites. The age of the zircons of 2.81 ± 0.05 Ga corresponds to the period of ultramafic magmatism within the Bug complex. Previously, this peak of endogenic activity was considered the stage of manifestation of metamorphism and magmatism of mafic composition.

Electron tunneling spectroscopy study of electrically active traps in AlGaN/GaN high electron mobility transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Jie, E-mail: jie.yang@yale.edu; Cui, Sharon; Ma, T. P.

2013-11-25

We investigate the energy levels of electron traps in AlGaN/GaN high electron mobility transistors by the use of electron tunneling spectroscopy. Detailed analysis of a typical spectrum, obtained in a wide gate bias range and with both bias polarities, suggests the existence of electron traps both in the bulk of AlGaN and at the AlGaN/GaN interface. The energy levels of the electron traps have been determined to lie within a 0.5 eV band below the conduction band minimum of AlGaN, and there is strong evidence suggesting that these traps contribute to Frenkel-Poole conduction through the AlGaN barrier.

Proteolysis controls endogenous substance P levels.

PubMed

Mitchell, Andrew J; Lone, Anna Mari; Tinoco, Arthur D; Saghatelian, Alan

2013-01-01

Substance P (SP) is a prototypical neuropeptide with roles in pain and inflammation. Numerous mechanisms regulate endogenous SP levels, including the differential expression of SP mRNA and the controlled secretion of SP from neurons. Proteolysis has long been suspected to regulate extracellular SP concentrations but data in support of this hypothesis is scarce. Here, we provide evidence that proteolysis controls SP levels in the spinal cord. Using peptidomics to detect and quantify endogenous SP fragments, we identify the primary SP cleavage site as the C-terminal side of the ninth residue of SP. If blocking this pathway increases SP levels, then proteolysis controls SP concentration. We performed a targeted chemical screen using spinal cord lysates as a proxy for the endogenous metabolic environment and identified GM6001 (galardin, ilomastat) as a potent inhibitor of the SP(1-9)-producing activity present in the tissue. Administration of GM6001 to mice results in a greater-than-three-fold increase in the spinal cord levels of SP, which validates the hypothesis that proteolysis controls physiological SP levels.

Changes in endogenous abscisic acid levels during dormancy release and maintenance of mature seeds: studies with the Cape Verde Islands ecotype, the dormant model of Arabidopsis thaliana.

PubMed

Ali-Rachedi, Sonia; Bouinot, Denise; Wagner, Marie-Hélène; Bonnet, Magda; Sotta, Bruno; Grappin, Philippe; Jullien, Marc

2004-07-01

Mature seeds of the Cape Verde Islands (Cvi) ecotype of Arabidopsis thaliana (L.) Heynh. show a very marked dormancy. Dormant (D) seeds completely fail to germinate in conditions that are favourable for germination whereas non-dormant (ND) seeds germinate easily. Cvi seed dormancy is alleviated by after-ripening, stratification, and also by nitrate or fluridone treatment. Addition of gibberellins to D seeds does not suppress dormancy efficiently, suggesting that gibberellins are not directly involved in the breaking of dormancy. Dormancy expression of Cvi seeds is strongly dependent on temperature: D seeds do not germinate at warm temperatures (20-27 degrees C) but do so easily at a low temperature (13 degrees C) or when a fluridone treatment is given to D seeds sown at high temperature. To investigate the role of abscisic acid (ABA) in dormancy release and maintenance, we measured the ABA content in both ND and D seeds imbibed using various dormancy-breaking conditions. It was found that dry D seeds contained higher amounts of ABA than dry ND after-ripened seeds. During early imbibition in standard conditions, there was a decrease in ABA content in both seeds, the rate of which was slower in D seeds. Three days after sowing, the ABA content in D seeds increased specifically and then remained at a high level. When imbibed with fluridone, nitrate or stratified, the ABA content of D seeds decreased and reached a level very near to that of ND seeds. In contrast, gibberellic acid (GA3) treatment caused a transient increase in ABA content. When D seeds were sown at low optimal temperature their ABA content also decreased to the level observed in ND seeds. The present study indicates that Cvi D and ND seeds can be easily distinguished by their ability to synthesize ABA following imbibition. Treatments used here to break dormancy reduced the ABA level in imbibed D seeds to the level observed in ND seeds, with the exception of GA3 treatment, which was active in promoting germination only when ABA synthesis was inhibited.

Light Regulation of Gibberellin Biosynthesis and Mode of Action.

PubMed

García-Martinez, José Luis; Gil, Joan

2001-12-01

Some phenotypic effects produced in plants by light are very similar to those induced by hormones. In this review, the light-gibberellin (GA) interaction in germination, de-etiolation, stem growth, and tuber formation (process regulated by GAs) are discussed. Germination of lettuce and Arabidopsis seeds depends on red irradiation (R), which enhances the expression of GA 3-oxidase genes (GA3ox) and leads to an increase in active GA content. De-etiolation of pea seedling alters the expression of GA20ox and GA3ox genes and induces a rapid decrease of GA1 content. Stem growth of green plants is also affected by diverse light irradiation characteristics. Low light intensity increases stem elongation and active GA content in pea and Brassica. Photoperiod controls active GA levels in long-day rosette (spinach and Silene) and in woody plants (Salix and hybrid aspen) by regulating different steps of GA biosynthesis, mainly through transcript levels of GA20ox and GA3ox genes. Light modulation of stem elongation in light-grown plants is controlled by phytochrome, which modifies GA biosynthesis and catabolism (tobacco, potato, cowpea, Arabidopsis) and GA-response (pea, cucumber, Arabidopsis). In Arabidopsis and tobacco, ATH1 (a gene encoding an homeotic transcription factor) is a positive mediator of a phyB-specific signal transduction cascade controlling GA levels by regulating the expression of GA20ox and GA3ox. Tuber formation in potato is controlled by photoperiod (through phyB) and GAs. Inductive short-day conditions alter the diurnal rhythm of GA20ox transcript abundance, and increases the expression of a new protein (PHOR1) that plays a role in the photoperiod-GA interaction.

Core-level photoemission investigation of atomic-fluorine adsorption on GaAs(110)

NASA Astrophysics Data System (ADS)

McLean, A. B.; Terminello, L. J.; McFeely, F. R.

1989-12-01

The adsorption of atomic F on the cleaved GaAs(110) surface has been studied with use of high-resolution core-level photoelectron spectroscopy by exposing the GaAs(110) surfaces to XeF2, which adsorbs dissociatively, leaving atomic F behind. This surface reaction produces two chemically shifted components in the Ga 3d core-level emission which are attributed to an interfacial monofluoride and a stable trifluoride reaction product, respectively. The As 3d core level develops only one chemically shifted component and from its exposure-dependent behavior it is attributed to an interfacial monofluoride. Least-squares analysis of the core-level line shapes revealed that (i) the F bonds to both the anion and the cation , (ii) the GaF3 component (characteristic of strong interfacial reaction) and the surface core-level shifted component (characteristic of a well ordered, atomically clean surface) are present together over a relatively large range of XeF2 exposures, and (iii) it is the initial disruption of the GaAs(110) surface that is the rate-limiting step in this surface reaction. These results are compared with similar studies of Cl and O adsorption on GaAs(110).

Unified mechanism of the surface Fermi level pinning in III-As nanowires.

PubMed

Alekseev, Prokhor A; Dunaevskiy, Mikhail S; Cirlin, George E; Reznik, Rodion R; Smirnov, Alexander N; Kirilenko, Demid A; Davydov, Valery Yu; Berkovits, Vladimir L

2018-08-03

Fermi level pinning at the oxidized (110) surfaces of III-As nanowires (GaAs, InAs, InGaAs, AlGaAs) is studied. Using scanning gradient Kelvin probe microscopy, we show that the Fermi level at oxidized cleavage surfaces of ternary Al x Ga 1-x As (0 ≤ x ≤ 0.45) and Ga x In 1-x As (0 ≤ x ≤ 1) alloys is pinned at the same position of 4.8 ± 0.1 eV with regard to the vacuum level. The finding implies a unified mechanism of the Fermi level pinning for such surfaces. Further investigation, performed by Raman scattering and photoluminescence spectroscopy, shows that photooxidation of the Al x Ga 1-x As and Ga x In 1-x As nanowires leads to the accumulation of an excess of arsenic on their crystal surfaces which is accompanied by a strong decrease of the band-edge photoluminescence intensity. We conclude that the surface excess arsenic in crystalline or amorphous forms is responsible for the Fermi level pinning at oxidized (110) surfaces of III-As nanowires.

Chronic treatment with glucocorticoids alters rat hippocampal and prefrontal cortical morphology in parallel with endogenous agmatine and arginine decarboxylase levels

PubMed Central

Zhu, Meng-Yang; Wang, Wei-Ping; Huang, Jingjing; Regunathan, Soundar

2009-01-01

In the present study, we examined the possible effect of chronic treatment with glucocorticoids on the morphology of the rat brain and levels of endogenous agmatine and arginine decarboxylase (ADC) protein, the enzyme essential for agmatine synthesis. Seven-day treatment with dexamethasone, at a dose (10 and 50 µg/kg/day) associated to stress effects contributed by glucocorticoids, did not result in obvious morphologic changes in the medial prefrontal cortex and hippocampus, as measured by immunocytochemical staining with β-tubulin III. However, 21-day treatment (50 µg/kg/day) produced noticeable structural changes such as the diminution and disarrangement of dendrites and neurons in these areas. Simultaneous treatment with agmatine (50 mg/kg/day) prevented these morphological changes. Further measurement with HPLC showed that endogenous agmatine levels in the prefrontal cortex and hippocampus were significantly increased after 7-day treatments with dexamethasone in a dose-dependent manner. On the contrary, 21-day treatment with glucocorticoids robustly reduced agmatine levels in these regions. The treatment-caused biphasic alterations of endogenous agmatine levels were also seen in the striatum and hypothalamus. Interestingly, treatment with glucocorticoids resulted in a similar change of ADC protein levels in most brain areas to endogenous agmatine levels: an increase after 7-day treatment versus a reduction after 21-day treatment. These results demonstrated that agmatine has neuroprotective effects against structural alterations caused by glucocorticoids in vivo. The parallel alterations in the endogenous agmatine levels and ADC expression in the brain after treatment with glucocorticoids indicate the possible regulatory effect of these stress hormones on the synthesis and metabolism of agmatine in vivo. PMID:17760863

Poole-Frenkel effect on electrical characterization of Al-doped ZnO films deposited on p-type GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Bohr-Ran; Liao, Chung-Chi; Ke, Wen-Cheng, E-mail: wcke@saturn.yzu.edu.tw

2014-03-21

This paper presents the electrical properties of Al-doped ZnO (AZO) films directly grown on two types of p-type GaN thin films. The low-pressure p-GaN thin films (LP-p-GaN) exhibited structural properties of high-density edge-type threading dislocations (TDs) and compensated defects (i.e., nitrogen vacancy). Compared with high-pressure p-GaN thin films (HP-p-GaN), X-ray photoemission spectroscopy of Ga 3d core levels indicated that the surface Fermi-level shifted toward the higher binding-energy side by approximately 0.7 eV. The high-density edge-type TDs and compensated defects enabled surface Fermi-level shifting above the intrinsic Fermi-level, causing the surface of LP-p-GaN thin films to invert to n-type semiconductor. A highlymore » nonlinear increase in leakage current regarding reverse-bias voltage was observed for AZO/LP-p-GaN. The theoretical fits for the reverse-bias voltage region indicated that the field-assisted thermal ionization of carriers from defect associated traps, which is known as the Poole-Frenkel effect, dominated the I-V behavior of AZO/LP-p-GaN. The fitting result estimated the trap energy level at 0.62 eV below the conduction band edge. In addition, the optical band gap increased from 3.50 eV for as-deposited AZO films to 3.62 eV for 300 °C annealed AZO films because of the increased carrier concentration. The increasing Fermi-level of the 300 °C annealed AZO films enabled the carrier transport to move across the interface into the LP-p-GaN thin films without any thermal activated energy. Thus, the Ohmic behavior of AZO contact can be achieved directly on the low-pressure p-GaN films at room temperature.« less

Poole-Frenkel effect on electrical characterization of Al-doped ZnO films deposited on p-type GaN

NASA Astrophysics Data System (ADS)

Huang, Bohr-Ran; Liao, Chung-Chi; Ke, Wen-Cheng; Chang, Yuan-Ching; Huang, Hao-Ping; Chen, Nai-Chuan

2014-03-01

This paper presents the electrical properties of Al-doped ZnO (AZO) films directly grown on two types of p-type GaN thin films. The low-pressure p-GaN thin films (LP-p-GaN) exhibited structural properties of high-density edge-type threading dislocations (TDs) and compensated defects (i.e., nitrogen vacancy). Compared with high-pressure p-GaN thin films (HP-p-GaN), X-ray photoemission spectroscopy of Ga 3d core levels indicated that the surface Fermi-level shifted toward the higher binding-energy side by approximately 0.7 eV. The high-density edge-type TDs and compensated defects enabled surface Fermi-level shifting above the intrinsic Fermi-level, causing the surface of LP-p-GaN thin films to invert to n-type semiconductor. A highly nonlinear increase in leakage current regarding reverse-bias voltage was observed for AZO/LP-p-GaN. The theoretical fits for the reverse-bias voltage region indicated that the field-assisted thermal ionization of carriers from defect associated traps, which is known as the Poole-Frenkel effect, dominated the I-V behavior of AZO/LP-p-GaN. The fitting result estimated the trap energy level at 0.62 eV below the conduction band edge. In addition, the optical band gap increased from 3.50 eV for as-deposited AZO films to 3.62 eV for 300 °C annealed AZO films because of the increased carrier concentration. The increasing Fermi-level of the 300 °C annealed AZO films enabled the carrier transport to move across the interface into the LP-p-GaN thin films without any thermal activated energy. Thus, the Ohmic behavior of AZO contact can be achieved directly on the low-pressure p-GaN films at room temperature.

Non-equilibrium Green's function calculation of AlGaAs-well-based and GaSb-based terahertz quantum cascade laser structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yasuda, H., E-mail: yasuda@nict.go.jp; Hosako, I.

2015-03-16

We investigate the performance of terahertz quantum cascade lasers (THz-QCLs) based on Al{sub x}Ga{sub 1−x}As/Al{sub y}Ga{sub 1−y}As and GaSb/AlGaSb material systems to realize higher-temperature operation. Calculations with the non-equilibrium Green's function method reveal that the AlGaAs-well-based THz-QCLs do not show improved performance, mainly because of alloy scattering in the ternary compound semiconductor. The GaSb-based THz-QCLs offer clear advantages over GaAs-based THz-QCLs. Weaker longitudinal optical phonon–electron interaction in GaSb produces higher peaks in the spectral functions of the lasing levels, which enables more electrons to be accumulated in the upper lasing level.

Treatment response in Kawasaki disease is associated with sialylation levels of endogenous but not therapeutic intravenous immunoglobulin G.

PubMed

Ogata, Shohei; Shimizu, Chisato; Franco, Alessandra; Touma, Ranim; Kanegaye, John T; Choudhury, Biswa P; Naidu, Natasha N; Kanda, Yutaka; Hoang, Long T; Hibberd, Martin L; Tremoulet, Adriana H; Varki, Ajit; Burns, Jane C

2013-01-01

Although intravenous immunoglobulin (IVIG) is highly effective in Kawasaki disease (KD), mechanisms are not understood and 10-20% of patients are treatment-resistant, manifesting a higher rate of coronary artery aneurysms. Murine models suggest that α2-6-linked sialic acid (α2-6Sia) content of IVIG is critical for suppressing inflammation. However, pro-inflammatory states also up-regulate endogenous levels of β-galactoside:α2-6 sialyltransferase-I (ST6Gal-I), the enzyme that catalyzes addition of α2-6Sias to N-glycans. We asked whether IVIG failures correlated with levels of α2-6Sia on infused IVIG or on the patient's own endogenous IgG. We quantified levels of α2-6Sia in infused IVIG and endogenous IgG from 10 IVIG-responsive and 10 resistant KD subjects using multiple approaches. Transcript levels of ST6GAL1, in patient whole blood and B cell lines were evaluated by RT-PCR. Plasma soluble (s)ST6Gal-I levels were measured by ELISA. There was no consistent difference in median sialylation levels of infused IVIG between groups. However, α2-6Sia levels in endogenous IgG, ST6GAL1 transcript levels, and ST6Gal-I protein in serum from IVIG-resistant KD subjects were lower than in responsive subjects at both pre-treatment and one-year time points (p <0.001, respectively). Our data indicate sialylation levels of therapeutic IVIG are unrelated to treatment response in KD. Rather, lower sialylation of endogenous IgG and lower blood levels of ST6GALI mRNA and ST6Gal-I enzyme predict therapy resistance. These differences were stable over time, suggesting a genetic basis. Because IVIG-resistance increases risk of coronary artery aneurysms, our findings have important implications for the identification and treatment of such individuals.

Treatment Response in Kawasaki Disease Is Associated with Sialylation Levels of Endogenous but Not Therapeutic Intravenous Immunoglobulin G

PubMed Central

Ogata, Shohei; Shimizu, Chisato; Franco, Alessandra; Touma, Ranim; Kanegaye, John T.; Choudhury, Biswa P.; Naidu, Natasha N.; Kanda, Yutaka; Hoang, Long T.; Hibberd, Martin L.; Tremoulet, Adriana H.; Varki, Ajit; Burns, Jane C.

2013-01-01

Objectives Although intravenous immunoglobulin (IVIG) is highly effective in Kawasaki disease (KD), mechanisms are not understood and 10-20% of patients are treatment-resistant, manifesting a higher rate of coronary artery aneurysms. Murine models suggest that α2-6-linked sialic acid (α2-6Sia) content of IVIG is critical for suppressing inflammation. However, pro-inflammatory states also up-regulate endogenous levels of β-galactoside:α2-6 sialyltransferase-I (ST6Gal-I), the enzyme that catalyzes addition of α2-6Sias to N-glycans. We asked whether IVIG failures correlated with levels of α2-6Sia on infused IVIG or on the patient’s own endogenous IgG. Methods We quantified levels of α2-6Sia in infused IVIG and endogenous IgG from 10 IVIG-responsive and 10 resistant KD subjects using multiple approaches. Transcript levels of ST6GAL1, in patient whole blood and B cell lines were evaluated by RT-PCR. Plasma soluble (s)ST6Gal-I levels were measured by ELISA. Results There was no consistent difference in median sialylation levels of infused IVIG between groups. However, α2-6Sia levels in endogenous IgG, ST6GAL1 transcript levels, and ST6Gal-I protein in serum from IVIG-resistant KD subjects were lower than in responsive subjects at both pre-treatment and one-year time points (p <0.001, respectively). Conclusions Our data indicate sialylation levels of therapeutic IVIG are unrelated to treatment response in KD. Rather, lower sialylation of endogenous IgG and lower blood levels of ST6GALI mRNA and ST6Gal-I enzyme predict therapy resistance. These differences were stable over time, suggesting a genetic basis. Because IVIG-resistance increases risk of coronary artery aneurysms, our findings have important implications for the identification and treatment of such individuals. PMID:24324693

Dormancy and germination: How does the crop seed decide?

PubMed

Shu, K; Meng, Y J; Shuai, H W; Liu, W G; Du, J B; Liu, J; Yang, W Y

2015-11-01

Whether seeds germinate or maintain dormancy is decided upon through very intricate physiological processes. Correct timing of these processes is most important for the plants life cycle. If moist conditions are encountered, a low dormancy level causes pre-harvest sprouting in various crop species, such as wheat, corn and rice, this decreases crop yield and negatively impacts downstream industrial processing. In contrast, a deep level of seed dormancy prevents normal germination even under favourable conditions, resulting in a low emergence rate during agricultural production. Therefore, an optimal seed dormancy level is valuable for modern mechanised agricultural systems. Over the past several years, numerous studies have demonstrated that diverse endogenous and environmental factors regulate the balance between dormancy and germination, such as light, temperature, water status and bacteria in soil, and phytohormones such as ABA (abscisic acid) and GA (gibberellic acid). In this updated review, we highlight recent advances regarding the molecular mechanisms underlying regulation of seed dormancy and germination processes, including the external environmental and internal hormonal cues, and primarily focusing on the staple crop species. Furthermore, future challenges and research directions for developing a full understanding of crop seed dormancy and germination are also discussed. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

Fermi level dependence of hydrogen diffusivity in GaN

NASA Astrophysics Data System (ADS)

Polyakov, A. Y.; Smirnov, N. B.; Pearton, S. J.; Ren, F.; Theys, B.; Jomard, F.; Teukam, Z.; Dmitriev, V. A.; Nikolaev, A. E.; Usikov, A. S.; Nikitina, I. P.

2001-09-01

Hydrogen diffusion studies were performed in GaN samples with different Fermi level positions. It is shown that, at 350 °C, hydrogen diffusion is quite fast in heavily Mg doped p-type material with the Fermi level close to Ev+0.15 eV, considerably slower in high-resistivity p-GaN(Zn) with the Fermi level Ev+0.9 eV, while for conducting and semi-insulating n-GaN samples with the Fermi level in the upper half of the band gap no measurable hydrogen diffusion could be detected. For these latter samples it is shown that higher diffusion temperature of 500 °C and longer times (50 h) are necessary to incorporate hydrogen to appreciable depth. These findings are in line with previously published theoretical predictions of the dependence of hydrogen interstitials formation in GaN on the Fermi level position.

Deep-levels in gallium arsenide for device applications

NASA Astrophysics Data System (ADS)

McManis, Joseph Edward

Defects in semiconductors have been studied for over 40 years as a diagnostic of the quality of crystal growth. In this thesis, we investigate GaAs deep-levels specifically intended for devices. This thesis summarizes our efforts to characterize the near-infrared photoluminescence from deep-levels, study optical transitions via absorption, and fabricate and characterize deep-level light-emitting diodes (LEDs). This thesis also describes the first tunnel diodes which explicitly make use of GaAs deep-levels. Photoluminescence measurements of GaAs deep-levels showed a broad peak around a wavelength extending from 1.0--1.7 mum, which includes important wavelengths for fiber-optic communications (1.3--1.55 mum). Transmission measurements show the new result that very little of the radiative emission is self-absorbed. We measured the deep-level photoluminescence at several temperatures. We are also the first to report the internal quantum efficiency associated with the deep-level transitions. We have fabricated LEDs that, utilize the optical transitions of GaAs deep-levels. The electroluminescence spectra showed a broad peak from 1.0--1.7 mum at low currents, but the spectrum exhibited a blue-shift as the current was increased. To improve device performance, we designed an AlGaAs layer into the structure of the LEDs. The AlGaAs barrier layer acts as a resistive barrier so that the holes in the p-GaAs layer are swept away from underneath the gold p-contact. The AlGaAs layer also reduces the blue-shift by acting as a potential barrier so that only higher-energy holes are injected. We found that the LEDs with AlGaAs were brighter at long wavelengths, which was a significant improvement. Photoluminescence measurements show that the spectral blue-shift is not due to sample heating. We have developed a new physical model to explain the blue-shift: it is caused by Coloumb charging of the deep-centers. We have achieved the first tunnel diodes with which specifically utilize deep-levels in low-temperature-grown (LTG) GaAs. Our devices show the largest ever peak current density in a GaAs tunnel diode at room temperature. Our devices also show significant room-temperature peak-to-valley current ratios. The shape of the current-voltage characteristic and the properties of the optical emission enable us to determine the peak and valley transport mechanisms.

A Role of Endogenous Progesterone in Stroke Cerebroprotection Revealed by the Neural-Specific Deletion of Its Intracellular Receptors.

PubMed

Zhu, Xiaoyan; Fréchou, Magalie; Liere, Philippe; Zhang, Shaodong; Pianos, Antoine; Fernandez, Neïké; Denier, Christian; Mattern, Claudia; Schumacher, Michael; Guennoun, Rachida

2017-11-08

Treatment with progesterone protects the male and female brain against damage after middle cerebral artery occlusion (MCAO). However, in both sexes, the brain contains significant amounts of endogenous progesterone. It is not known whether endogenously produced progesterone enhances the resistance of the brain to ischemic insult. Here, we used steroid profiling by gas chromatography-tandem mass spectrometry (GC-MS/MS) for exploring adaptive and sex-specific changes in brain levels of progesterone and its metabolites after MCAO. We show that, in the male mouse brain, progesterone is mainly metabolized via 5α-reduction leading to 5α-dihydroprogesterone (5α-DHP), also a progesterone receptor (PR) agonist ligand in neural cells, then to 3α,5α-tetrahydroprogesterone (3α,5α-THP). In the female mouse brain, levels of 5α-DHP and 3α,5α-THP are lower and levels of 20α-DHP are higher than in males. After MCAO, levels of progesterone and 5α-DHP are upregulated rapidly to pregnancy-like levels in the male but not in the female brain. To assess whether endogenous progesterone and 5α-DHP contribute to the resistance of neural cells to ischemic damage, we inactivated PR selectively in the CNS. Deletion of PR in the brain reduced its resistance to MCAO, resulting in increased infarct volumes and neurological deficits in both sexes. Importantly, endogenous PR ligands continue to protect the brain of aging mice. These results uncover the unexpected importance of endogenous progesterone and its metabolites in cerebroprotection. They also reveal that the female reproductive hormone progesterone is an endogenous cerebroprotective neurosteroid in both sexes. SIGNIFICANCE STATEMENT The brain responds to injury with protective signaling and has a remarkable capacity to protect itself. We show here that, in response to ischemic stroke, levels of progesterone and its neuroactive metabolite 5α-dihydroprogesterone are upregulated rapidly in the male mouse brain but not in the female brain. An important role of endogenous progesterone in cerebroprotection was demonstrated by the conditional inactivation of its receptor in neural cells. These results show the importance of endogenous progesterone, its metabolites, and neural progesterone receptors in acute cerebroprotection after stroke. This new concept could be exploited therapeutically by taking into account the progesterone status of patients and by supplementing and reinforcing endogenous progesterone signaling for attaining its full cerebroprotective potential. Copyright © 2017 the authors 0270-6474/17/3710998-23$15.00/0.

The molecular basis of low activity levels of coagulation factor VII: a Brazilian cohort.

PubMed

Rabelo, F Y; Jardim, L L; Landau, M B; Gadelha, T; Corrêa, M F B; Pereira, I F M; Rezende, S M

2015-09-01

Inherited factor VII (FVII) deficiency is the most common among the rare bleeding disorders. It is transmitted as an autosomal recessive inheritance, due to mutations in the FVII gene (F7). Molecular studies of FVII deficiency are rare in non-Caucasian populations. The aim of the study was to evaluate the molecular basis behind low levels of FVII activity (FVII:C) levels in a cohort of Brazilian patients. A total of 34 patients with low FVII levels were clinically evaluated and submitted to laboratory tests, among these, prothrombin time and FVII:C, with different thromboplastins. All exons and intron/exon boundaries of F7 were amplified and sequenced. A total of 14 genetic alterations were identified, of which six were described previously, c.1091G>A, c.1151C>T, c.-323_-313insCCTATATCCT, c.285G>A, c.525C>T, c.1238G>A and eight (54.0%) and eight were new, c.128G>A, c.252C>T, c.348G>A, c.417G>A, c.426G>A, c.745_747delGTG, c.843G>A and c.805+52C>T. In addition to the mutation c.1091G>A, known as FVII Padua, the mutation c.1151C>T also presented discrepant FVII:C levels when tested with human and rabbit brain thromboplastin. There was no association between phenotype and genotype. Most of the identified genetic alterations found were polymorphisms. Low levels of FVII:C in this population were mostly related to polymorphisms in F7 and associated with a mild clinical phenotype. Mutation c.1151C>T was associated with discrepant levels of FVII:C using different thromboplastins, such as reported with FVII Padua. © 2015 John Wiley & Sons Ltd.

[Effects of shading on endogenous hormones regulation in kernel development of summer maize in the field].

PubMed

Cui, Hai-Yan; Jin, Li-Bin; Li, Bo; Dong, Shu-Ting; Liu, Peng; Zhao, Bin; Zhang, Ji-Wang

2014-05-01

Taking 3 maize hybrids, Zhenjie 2 (ZJ2), Denghai 605 (DH605) and Zhengdan 958 (ZD958) as test materials, the effects of shading on the physiological function of endogenous hormones during grain formation of summer maize were investigated in the field. The ambient sunshine treatment was used as the control (CK) and 3 shading treatments with a shading degree of 60% were designed in growth periods ranging from tasseling to maturity (S1), from jointing to tasseling stage (S2) and whole growing period (S3), respectively. Results showed that the total floret number, filament number and pollination floret number decreased after shading in comparison with CK, and aborted seeds increased accordingly. The kernels per ear showed an order of CK > S2 > S > S3, and those of S1, S2 and S3 were 18.9%, 43.7% and 80.8% lower than that of CK. The IAA, GA and ZR contents of normal grain in the shading treatments were lower than in CK, while the ABA content was opposite. The same hormone change with grain growth in all treatments presented a similar trend. Compared to normal grains, the maximum value of IAA content in aborted grains shifted from the 20th day to the 10th day after pollination, with less IAA accumulation and rapid reduction, and the contents of GA and ZR decreased significantly, while that of ABA was still high at the 20th day after pollination. Therefore, the effects of shading on hormone contents in grains might lead to grain abortion and yield reduction.

Effects of hydrogen treatment on ohmic contacts to p-type GaN films

NASA Astrophysics Data System (ADS)

Huang, Bohr-Ran; Chou, Chia-Hui; Ke, Wen-Cheng; Chou, Yi-Lun; Tsai, Chia-Lung; Wu, Meng-chyi

2011-06-01

This study investigated the effects of hydrogen (H 2) treatment on metal contacts to Mg-doped p-GaN films by Hall-effect measurement, current-voltage ( I- V) analyzer and X-ray photoemission spectra (XPS). The interfacial oxide layer on the p-GaN surface was found to be the main reason for causing the nonlinear I- V behavior of the untreated p-GaN films. The increased nitrogen vacancy (V N) density due to increased GaN decomposition rate at high-temperature hydrogen treatment is believed to form high density surface states on the surface of p-GaN films. Compared to untreated p-GaN films, the surface Fermi level determined by the Ga 2p core-level peak on 1000 °C H 2-treated p-GaN films lies about ˜2.1 eV closer to the conduction band edge (i.e., the surface inverted to n-type behavior). The reduction in barrier height due to the high surface state density pinned the surface Fermi level close to the conduction band edge, and allowed the electrons to easily flow over the barrier from the metal into the p-GaN films. Thus, a good ohmic contact was achieved on the p-GaN films by the surface inversion method.

The effect of Ga vacancies on the defect and magnetic properties of Mn-doped GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Joongoo; Chang, K. J.; Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea and Korea Institute for Advanced Study, Seoul 130-722

2007-10-15

We perform first-principles theoretical calculations to investigate the effect of the presence of Ga vacancy on the defect and magnetic properties of Mn-doped GaN. When a Ga vacancy (V{sub Ga}) is introduced to the Mn ions occupying the Ga lattice sites, a charge transfer occurs from the Mn d band to the acceptor levels of V{sub Ga}, and strong Mn-N bonds are formed between the Mn ion and the N atoms in the neighborhood of V{sub Ga}. The charge transfer and chemical bonding effects significantly affect the defect and magnetic properties of Mn-doped GaN. In a Mn-V{sub Ga} complex, whichmore » consists of a Ga vacancy and one Mn ion, the dangling bond orbital of the N atom involved in the Mn-N bond is electrically deactivated, and the remaining dangling bond orbitals of V{sub Ga} lead to the shallowness of the defect level. When a Ga vacancy forms a complex with two Mn ions located at a distance of about 6 A, which corresponds to the percolation length in determining the Curie temperature in diluted Mn-doped GaN, the Mn d band is broadened and the density of states at the Fermi level is reduced due to two strong Mn-N bonds. Although the broadening and depopulation of the Mn d band weaken the ferromagnetic stability between the Mn ions, the ferromagnetism is still maintained because of the lack of antiferromagnetic superexchange interactions at the percolation length.« less

Carrier quenching in InGaP/GaAs double heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wells, Nathan P., E-mail: nathan.p.wells@aero.org; Driskell, Travis U.; Hudson, Andrew I.

2015-08-14

Photoluminescence measurements on a series of GaAs double heterostructures demonstrate a rapid quenching of carriers in the GaAs layer at irradiance levels below 0.1 W/cm{sup 2} in samples with a GaAs-on-InGaP interface. These results indicate the existence of non-radiative defect centers at or near the GaAs-on-InGaP interface, consistent with previous reports showing the intermixing of In and P when free As impinges on the InGaP surface during growth. At low irradiance, these defect centers can lead to sub-ns carrier lifetimes. The defect centers involved in the rapid carrier quenching can be saturated at higher irradiance levels and allow carrier lifetimes tomore » reach hundreds of nanoseconds. To our knowledge, this is the first report of a nearly three orders of magnitude decrease in carrier lifetime at low irradiance in a simple double heterostructure. Carrier quenching occurs at irradiance levels near the integrated Air Mass Zero (AM0) and Air Mass 1.5 (AM1.5) solar irradiance. Additionally, a lower energy photoluminescence band is observed both at room and cryogenic temperatures. The temperature and time dependence of the lower energy luminescence is consistent with the presence of an unintentional InGaAs or InGaAsP quantum well that forms due to compositional mixing at the GaAs-on-InGaP interface. Our results are of general interest to the photovoltaic community as InGaP is commonly used as a window layer in GaAs based solar cells.« less

Interface trap of p-type gate integrated AlGaN/GaN heterostructure field effect transistors

NASA Astrophysics Data System (ADS)

Kim, Kyu Sang

2017-09-01

In this work, the impact of trap states at the p-(Al)GaN/AlGaN interface has been investigated for the normally-off mode p-(Al)GaN/AlGaN/GaN heterostructure field-effect transistors (HFETs) by means of frequency dependent conductance. From the current-voltage (I-V) measurement, it was found that the p-AlGaN gate integrated device has higher drain current and lower gate leakage current compared to the p-GaN gate integrated device. We obtained the interface trap density and the characteristic time constant for the p-type gate integrated HFETs under the forward gate voltage of up to 6 V. As a result, the interface trap density (characteristic time constant) of the p-GaN gate device was lower (longer) than that of the p-AlGaN. Furthermore, it was analyzed that the trap state energy level of the p-GaN gate device was located at the shallow level relative to the p-AlGaN gate device, which accounts for different gate leakage current of each devices.

Expression patterns of ABA and GA metabolism genes and hormone levels during rice seed development and imbibition: a comparison of dormant and non-dormant rice cultivars.

PubMed

Liu, Yang; Fang, Jun; Xu, Fan; Chu, Jinfang; Yan, Cunyu; Schläppi, Michael R; Wang, Youping; Chu, Chengcai

2014-06-20

Seed dormancy is an important agronomic trait in cereals. Using deep dormant (N22), medium dormant (ZH11), and non-dormant (G46B) rice cultivars, we correlated seed dormancy phenotypes with abscisic acid (ABA) and gibberellin (GA) metabolism gene expression profiles and phytohormone levels during seed development and imbibition. A time course analysis of ABA and GA content during seed development showed that N22 had a high ABA level at early and middle seed developmental stages, while at late developmental stage it declined to the level of ZH11; however, its ABA/GA ratio maintained at a high level throughout seed development. By contrast, G46B had the lowest ABA content during seed development though at early developmental stage its ABA level was close to that of ZH11, and its ABA/GA ratio peaked at late developmental stage that was at the same level of ZH11. Compared with N22 and G46B, ZH11 had an even and medium ABA level during seed development and its ABA/GA ratio peaked at the middle developmental stage. Moreover, the seed development time-point having high ABA/GA ratio also had relatively high transcript levels for key genes in ABA and GA metabolism pathways across three cultivars. These indicated that the embryo-imposed dormancy has been induced before the late developmental stage and is determined by ABA/GA ratio. A similar analysis during seed imbibition showed that ABA was synthesized in different degrees for the three cultivars. In addition, water uptake assay for intact mature seeds suggested that water could permeate through husk barrier into seed embryo for all three cultivars; however, all three cultivars showed distinct colors by vanillin-staining indicative of the existence of flavans in their husks, which are dormancy inhibition compounds responsible for the husk-imposed dormancy. Copyright © 2014. Published by Elsevier Ltd.

Exogenously applied spermidine alleviates photosynthetic inhibition under drought stress in maize (Zea mays L.) seedlings associated with changes in endogenous polyamines and phytohormones.

PubMed

Li, Lijie; Gu, Wanrong; Li, Jing; Li, Congfeng; Xie, Tenglong; Qu, Danyang; Meng, Yao; Li, Caifeng; Wei, Shi

2018-05-15

Drought stress (DS) is a major environmental factor limiting plant growth and crop productivity worldwide. It has been established that exogenous spermidine (Spd) stimulates plant tolerance to DS. The effects of exogenous Spd on plant growth, photosynthetic performance, and chloroplast ultrastructure as well as changes in endogenous polyamines (PAs) and phytohormones were investigate in DS-resistant (Xianyu 335) and DS-sensitive (Fenghe 1) maize seedlings under well-watered and DS treatments. Exogenous Spd alleviated the stress-induced reduction in growth, photosynthetic pigment content, photosynthesis rate (P n ) and photochemical quenching (q P ) parameters, including the maximum photochemistry efficiency of photosystem II (PSII) (F v /F m ), PSII operating efficiency (ФPSII), and qP coefficient. Exogenous Spd further enhanced stress-induced elevation in non-photochemical quenching (NPQ) and the de-epoxidation state of the xanthophyll cycle (DEPS). Microscopic analysis revealed that seedlings displayed a more ordered arrangement of chloroplast ultrastructure upon Spd application during DS. Exogenous Spd increased the endogenous PA concentrations in the stressed plants. Additionally, exogenous Spd increased indoleacetic acid (IAA), zeatin riboside (ZR) and gibberellin A 3 (GA 3 ) and decreased salicylic acid (SA) and jasmonate (JA) concentrations under DS. These results indicate that exogenous Spd can alleviate the growth inhibition and damage to the structure and function of the photosynthetic apparatus caused by DS and that this alleviation may be associated with changes in endogenous PAs and phytohormones. This study contributes to advances in the knowledge of Spd-induced drought tolerance. Copyright © 2018. Published by Elsevier Masson SAS.

/sup 67/Ga citrate scanning and serum angiotensin converting enzyme levels in sarcoidosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, R.G.; Bekerman, C.; Sicilian, L.

1982-09-01

/sup 67/Ga citrate scans and serum angiotensin converting enzyme (ACE) levels were obtained in 54 patients with sarcoidosis and analyzed in relation to clinical manifestations. /sup 67/Ga scans were abnormal in 97% of patients with clinically active disease (n . 30) and in 71% of patients with inactive disease (n . 24). Serum ACE levels were abnormally high (2 standard deviations above the control mean) in 73% of patients with clinically active disease and in 54% of patients with inactive disease. Serum ACE levels correlated significantly with /sup 67/Ga uptake score (r..436; p less than .005). The frequency of abnormalmore » /sup 67/Ga scans and elevated serum ACE levels suggests that inflammatory activity with little or no clinical expression is common in sarcoidosis. Abnormal /sup 67/Ga scans were highly sensitive (97%) but had poor specificity (29%) to clinical disease activity. The accuracy of negative prediction of clinical activity by normal scans (87%) was better than the accuracy of positive prediction of clinical activity by abnormal scans (63%). /sup 67/Ga scans can be used to support the clinical indentification of inactive sacoidosis.« less

Defect interactions in GaAs single crystals

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Lagowski, J.

1984-01-01

The two-sublattice structural configuration of GaAs and deviations from stoichiometry render the generation and interaction of electrically active point defects (and point defect complexes) critically important for device applications and very complex. Of the defect-induced energy levels, those lying deep into the energy band are very effective lifetime ""killers". The level 0.82 eV below the condition band, commonly referred to as EL2, is a major deep level, particularly in melt-grown GaAs. This level is associated with an antisite defect complex (AsGa - VAS). Possible mechanisms of its formation and its annihilation were further developed.

Effect of antimony on the deep-level traps in GaInNAsSb thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Islam, Muhammad Monirul, E-mail: islam.monir.ke@u.tsukuba.ac.jp; Miyashita, Naoya; Ahsan, Nazmul

2014-09-15

Admittance spectroscopy has been performed to investigate the effect of antimony (Sb) on GaInNAs material in relation to the deep-level defects in this material. Two electron traps, E1 and E2 at an energy level 0.12 and 0.41 eV below the conduction band (E{sub C}), respectively, were found in undoped GaInNAs. Bias-voltage dependent admittance confirmed that E1 is an interface-type defect being spatially localized at the GaInNAs/GaAs interface, while E2 is a bulk-type defect located around mid-gap of GaInNAs layer. Introduction of Sb improved the material quality which was evident from the reduction of both the interface and bulk-type defects.

Proteolysis Controls Endogenous Substance P Levels

PubMed Central

Mitchell, Andrew J.; Lone, Anna Mari; Tinoco, Arthur D.; Saghatelian, Alan

2013-01-01

Substance P (SP) is a prototypical neuropeptide with roles in pain and inflammation. Numerous mechanisms regulate endogenous SP levels, including the differential expression of SP mRNA and the controlled secretion of SP from neurons. Proteolysis has long been suspected to regulate extracellular SP concentrations but data in support of this hypothesis is scarce. Here, we provide evidence that proteolysis controls SP levels in the spinal cord. Using peptidomics to detect and quantify endogenous SP fragments, we identify the primary SP cleavage site as the C-terminal side of the ninth residue of SP. If blocking this pathway increases SP levels, then proteolysis controls SP concentration. We performed a targeted chemical screen using spinal cord lysates as a proxy for the endogenous metabolic environment and identified GM6001 (galardin, ilomastat) as a potent inhibitor of the SP 1–9-producing activity present in the tissue. Administration of GM6001 to mice results in a greater-than-three-fold increase in the spinal cord levels of SP, which validates the hypothesis that proteolysis controls physiological SP levels. PMID:23894327

Gibberellin Regulation of Fruit Set and Growth in Tomato1[W

PubMed Central

Serrani, Juan Carlos; Sanjuán, Rafael; Ruiz-Rivero, Omar; Fos, Mariano; García-Martínez, José Luis

2007-01-01

The role of gibberellins (GAs) in tomato (Solanum lycopersicum) fruit development was investigated. Two different inhibitors of GA biosynthesis (LAB 198999 and paclobutrazol) decreased fruit growth and fruit set, an effect reversed by GA3 application. LAB 198999 reduced GA1 and GA8 content, but increased that of their precursors GA53, GA44, GA19, and GA20 in pollinated fruits. This supports the hypothesis that GA1 is the active GA for tomato fruit growth. Unpollinated ovaries developed parthenocarpically in response to GA3 > GA1 = GA4 > GA20, but not to GA19, suggesting that GA 20-oxidase activity was limiting in unpollinated ovaries. This was confirmed by analyzing the effect of pollination on transcript levels of SlCPS, SlGA20ox1, -2, and -3, and SlGA3ox1 and -2, encoding enzymes of GA biosynthesis. Pollination increased transcript content of SlGA20ox1, -2, and -3, and SlCPS, but not of SlGA3ox1 and -2. To investigate whether pollination also altered GA inactivation, full-length cDNA clones of genes encoding enzymes catalyzing GA 2-oxidases (SlGA2ox1, -2, -3, -4, and -5) were isolated and characterized. Transcript levels of these genes did not decrease early after pollination (5-d-old fruits), but transcript content reduction of all of them, mainly of SlGA2ox2, was found later (from 10 d after anthesis). We conclude that pollination mediates fruit set by activating GA biosynthesis mainly through up-regulation of GA20ox. Finally, the phylogenetic reconstruction of the GA2ox family clearly showed the existence of three gene subfamilies, and the phylogenetic position of SlGA2ox1, -2, -3, -4, and -5 was established. PMID:17660355

Modeling the interaction of binary and ternary mixtures of estradiol with bisphenol A and bisphenol A F in an in vitro estrogen mediated transcriptional activation assay (T47D-KBluc)

EPA Science Inventory

Exposure to xenoestrogens occurs against a backdrop to physiological levels of endogenous estrogens. Endogenous estrogen levels vary from low levels in early childhood to high levels during pregnancy and in young women. For example, children have circulating E2concentrations rang...

Modeling the interaction of binary and ternary mixtures of estradiol with bisphenol A and bisphenol A F in an in vitro estrogen mediated transcriptional activation assay (T47D-KBluc).

EPA Science Inventory

Humans are concurrently exposed to xenoestrogens and to physiological levels of endogenous estrogens. Endogenous estrogen levels vary from low levels in infants to high levels during pregnancy and in young women. However, few studies have addressed how xenoestrogens interact with...

Studies on the pathogenesis of fever. IX. Characteristics of endogenous serum pyrogen and mechanisms governing its release.

PubMed

PETERSDORF, R G; KEENE, W R; BENNETT, I L

1957-12-01

The "endogenous serum pyrogen" that appears in the circulating blood after a single intravenous injection of endotoxin does not produce leukopenia in normal animals, fails to provoke the local Shwartzman reaction, and elicits no "tolerance" when injected daily. Suppression of the febrile response to endotoxin by prednisone does not prevent the appearance of pyrogen in the blood. Animals given large amounts of endotoxin daily continue to respond with high fevers despite failure of endogenous serum pyrogen to appear in detectable amounts after the first two or three injections. Analysis of the response to daily injections shows clearly that the fever during the first 2 hours after administration of endotoxin is unrelated to levels of endogenous serum pyrogen; in contrast, the magnitude of the fever after the 2nd hour correlates well with endogenous pyrogen in some instances. The leukopenic response to endotoxin could not be correlated with the appearance of endogenous serum pyrogen. The differences between endotoxin and endogenous pyrogen and the similarities between leukocyte extracts (sterile exudates) and endogenous pyrogen are summarized and discussed. Dissociation of the febrile response to bacterial endotoxin and levels of endogenous serum pyrogen are discussed and it is concluded that a mechanism involving both direct and indirect action of endotoxins offers the best explanation for the pyrogenic action of these bacterial products.

Nutritional Control of Regreening and Degreening in Citrus Peel Segments 1

PubMed Central

Huff, Albert

1983-01-01

A method for reversibly regreening and degreening citrus epicarp in vitro using peel segments was developed. Peel segments from mature degreened fruit promptly regreened when kept in light upon agar medium containing low (15 millimolar) concentrations of sucrose. Higher concentrations of sucrose inhibited this regreening, but NO3− and certain amino acids included in the media overcame the inhibition by sucrose. However, l-serine strongly inhibited regreening. In the presence of nitrogen, sucrose promoted regreening. Peel segments from green fruit remained green on media with low concentrations of sucrose and on media with high concentrations of sucrose and 60 millimolar KNO3, but degreened in response to high concentrations of sucrose in the absence of nitrogen. Nitrate overcame the degreening effects of high sucrose concentrations in both light and dark. Peel segments were reversibly degreened and regreened by transferring the segments between appropriate media. Nitrate in the media markedly reduced the levels of endogenous sugars in the epicarp and increased endogenous amino acid levels. Sucrose in the media increased endogenous sugar levels and, in the presence of nitrate, increased endogenous amino acid levels. In the absence of nitrogen, high sucrose concentrations reduced endogenous amino acid concentrations. PMID:16663202

Detection of deep-level defects and reduced carrier concentration in Mg-ion-implanted GaN before high-temperature annealing

NASA Astrophysics Data System (ADS)

Akazawa, Masamichi; Yokota, Naoshige; Uetake, Kei

2018-02-01

We report experimental results for the detection of deep-level defects in GaN after Mg ion implantation before high-temperature annealing. The n-type GaN samples were grown on GaN free-standing substrates by metalorganic vapor phase epitaxy. Mg ions were implanted at 50 keV with a small dosage of 1.5×1011 cm-2, which did not change the conduction type of the n-GaN. By depositing Al2O3 and a Ni/Au electrode onto the implanted n-GaN, metal-oxide-semiconductor (MOS) diodes were fabricated and tested. The measured capacitance-voltage (C-V) characteristics showed a particular behavior with a plateau region and a region with an anomalously steep slope. Fitting to the experimental C-V curves by simulation showed the existence of deep-level defects and a reduction of the carrier concentration near the GaN surface. By annealing at 800oC, the density of the deep-level defects was reduced and the carrier concentration partially recovered.

Origins of Fermi-level pinning on GaN and InN polar and nonpolar surfaces

NASA Astrophysics Data System (ADS)

Segev, D.; Van de Walle, C. G.

2006-10-01

Using band structure and total energy methods, we study the atomic and electronic structures of the polar (+c and - c plane) and nonpolar (a and m plane) surfaces of GaN and InN. We identify two distinct microscopic origins for Fermi-level pinning on GaN and InN, depending on surface stoichiometry and surface polarity. At moderate Ga/N ratios unoccupied gallium dangling bonds pin the Fermi level on n-type GaN at 0.5 0.7 eV below the conduction-band minimum. Under highly Ga-rich conditions metallic Ga adlayers lead to Fermi-level pinning at 1.8 eV above the valence-band maximum. We also explain the source of the intrinsic electron accumulation that has been universally observed on polar InN surfaces. It is caused by In-In bonds leading to occupied surface states above the conduction-band minimum. We predict that such a charge accumulation will be absent on the nonpolar surfaces of InN, when prepared under specific conditions.

Gibberellins inhibit adventitious rooting in hybrid aspen and Arabidopsis by affecting auxin transport.

PubMed

Mauriat, Mélanie; Petterle, Anna; Bellini, Catherine; Moritz, Thomas

2014-05-01

Knowledge of processes involved in adventitious rooting is important to improve both fundamental understanding of plant physiology and the propagation of numerous plants. Hybrid aspen (Populus tremula × tremuloïdes) plants overexpressing a key gibberellin (GA) biosynthesis gene (AtGA20ox1) grow rapidly but have poor rooting efficiency, which restricts their clonal propagation. Therefore, we investigated the molecular basis of adventitious rooting in Populus and the model plant Arabidopsis. The production of adventitious roots (ARs) in tree cuttings is initiated from the basal stem region, and involves the interplay of several endogenous and exogenous factors. The roles of several hormones in this process have been characterized, but the effects of GAs have not been fully investigated. Here, we show that a GA treatment negatively affects the numbers of ARs produced by wild-type hybrid aspen cuttings. Furthermore, both hybrid aspen plants and intact Arabidopsis seedlings overexpressing AtGA20ox1, PttGID1.1 or PttGID1.3 genes (with a 35S promoter) produce few ARs, although ARs develop from the basal stem region of hybrid aspen and the hypocotyl of Arabidopsis. In Arabidopsis, auxin and strigolactones are known to affect AR formation. Our data show that the inhibitory effect of GA treatment on adventitious rooting is not mediated by perturbation of the auxin signalling pathway, or of the strigolactone biosynthetic and signalling pathways. Instead, GAs appear to act by perturbing polar auxin transport, in particular auxin efflux in hybrid aspen, and both efflux and influx in Arabidopsis. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

The Glycated Albumin (GA) to HbA1c Ratio Reflects Shorter-Term Glycemic Control than GA: Analysis of Patients with Fulminant Type 1 Diabetes.

PubMed

Koga, Masafumi; Inada, Shinya; Nakao, Taisei; Kawamori, Ryuzo; Kasayama, Soji

2017-01-01

Glycated albumin (GA) reflects shorter-term glycemic control than HbA1c. We have reported that HbA1c is paradoxically increased in diabetic patients whose glycemic control deteriorated before ameliorating. In this study, we analyzed paradoxical increases of glycemic control indicators after treatment in patients with fulminant type 1 diabetes (FT1D). We also investigated whether the GA/HbA1c ratio may reflect shorter-term glycemic control than GA. Five FT1D patients whose post-treatment HbA1c and GA levels were measured were enrolled. We also used a formula to estimate HbA1c and GA from the fictitious models of changes in plasma glucose in FT1D patients. In this model, the periods during which HbA1c, GA, and the GA/HbA1c ratio were higher than at the first visit were compared. In addition, the half-life for the GA/HbA1c ratio was calculated in accordance with the half-lives for HbA1c and GA (36 and 14 days, respectively). In all FT1D patients, HbA1c levels 2-4 weeks after treatment were increased, with three patients (60%) experiencing an increase of GA levels. In contrast, an increase of the GA/HbA1c ratio was observed in only one patient. In all of the different models of changes in plasma glucose in FT1D patients, the length of time during which the values were higher than at the first visit was in the order of HbA1c > GA > GA/HbA1c ratio. The half-life for the GA/HbA1c ratio was 9 days, shorter than GA. These findings suggest that the GA/HbA1c ratio reflects shorter-term glycemic control than GA. © 2016 Wiley Periodicals, Inc.

STUDIES ON THE PATHOGENESIS OF FEVER

PubMed Central

Petersdorf, Robert G.; Keene, Willis R.; Bennett, Ivan L.

1957-01-01

The "endogenous serum pyrogen" that appears in the circulating blood after a single intravenous injection of endotoxin does not produce leukopenia in normal animals, fails to provoke the local Shwartzman reaction, and elicits no "tolerance" when injected daily. Suppression of the febrile response to endotoxin by prednisone does not prevent the appearance of pyrogen in the blood. Animals given large amounts of endotoxin daily continue to respond with high fevers despite failure of endogenous serum pyrogen to appear in detectable amounts after the first two or three injections. Analysis of the response to daily injections shows clearly that the fever during the first 2 hours after administration of endotoxin is unrelated to levels of endogenous serum pyrogen; in contrast, the magnitude of the fever after the 2nd hour correlates well with endogenous pyrogen in some instances. The leukopenic response to endotoxin could not be correlated with the appearance of endogenous serum pyrogen. The differences between endotoxin and endogenous pyrogen and the similarities between leukocyte extracts (sterile exudates) and endogenous pyrogen are summarized and discussed. Dissociation of the febrile response to bacterial endotoxin and levels of endogenous serum pyrogen are discussed and it is concluded that a mechanism involving both direct and indirect action of endotoxins offers the best explanation for the pyrogenic action of these bacterial products. PMID:13481245

Transcriptional elements from the human SP-C gene direct expression in the primordial respiratory epithelium of transgenic mice.

PubMed

Wert, S E; Glasser, S W; Korfhagen, T R; Whitsett, J A

1993-04-01

Transgenic animals bearing a chimeric gene containing 5'-flanking regions of the human surfactant protein C (SP-C) gene ligated to the bacterial chloramphenicol acetyltransferase (CAT) gene were analyzed by in situ hybridization histochemistry to determine the temporal and spatial distribution of transgene expression during organogenesis of the murine lung. Ontogenic expression of the SP-C-CAT gene was compared to that of the endogenous SP-C gene and to the Clara cell CC10 gene. High levels of SP-C-CAT expression were observed as early as Day 10 of gestation in epithelial cells of the primordial lung buds. Low levels of endogenous SP-C mRNA were detected a day later, but only in the more distal epithelial cells of the newly formed, primitive, lobar bronchi. On Gestational Days 13 through 16, transcripts for both the endogenous and chimeric gene were restricted to distal epithelial elements of the branching bronchial tubules and were no longer detected in the more proximal regions of the bronchial tree. Although high levels of SP-C-CAT expression were maintained throughout organogenesis, endogenous SP-C expression increased dramatically on Gestational Day 15, coincident with acinar tubule differentiation at the lung periphery. Low levels of endogenous CC10 expression were detected by Gestational Day 16 in both lobar and segmental bronchi. By the time of birth, CC10 transcripts were expressed at high levels in the trachea and at all levels of the bronchial tree; endogenous SP-C mRNA was restricted to epithelial cells of the terminal alveolar saccules; and SP-C-CAT expression was now detected in both alveolar and bronchiolar epithelial cells. These results indicate that (1) cis-acting regulatory elements of the human SP-C gene can direct high levels of foreign gene expression to epithelial cells of the embryonic mouse lung; (2) expression of the human SP-C-CAT chimeric gene is developmentally regulated, exhibiting a morphogenic expression pattern similar, but not identical, to that of the endogenous murine SP-C gene; (3) the embryonic expression of endogenous SP-C and chimeric SP-C-CAT transcripts identifies progenitor cells of the distal respiratory epithelium; and (4) differentiation of bronchial epithelium is coincident with loss of SP-C expression and subsequent acquisition of CC10 expression in proximal regions of the developing bronchial tubules.

PLASMA OXYTOCIN LEVELS PREDICT SOCIAL CUE RECOGNITION IN INDIVIDUALS WITH SCHIZOPHRENIA

PubMed Central

Strauss, Gregory P.; Keller, William R.; Koenig, James I.; Gold, James M.; Frost, Katherine H.; Buchanan, Robert W.

2015-01-01

Lower endogenous levels of the neuropeptide oxytocin may be an important biological predictor of social cognition impairments in schizophrenia (SZ). Prior studies have demonstrated that lower-level social cognitive processes (e.g., facial affect perception) are significantly associated with reduced plasma oxytocin levels in SZ; however, it is unclear whether higher-level social cognition, which requires inferential processes and knowledge not directly presented in the stimulus, is associated with endogenous oxytocin. The current study explored the association between endogenous oxytocin levels and lower- and higher-level social cognition in 40 individuals diagnosed with SZ and 22 demographically matched healthy controls (CN). All participants received the Social Cue Recognition Test (SCRT), which presents participants with videotaped interpersonal vignettes and subsequent true/false questions related to concrete or abstract aspects of social interactions in the vignettes. Results indicated that SZ had significantly higher plasma oxytocin concentrations than CN. SZ and CN did not differ on SCRT hits, but SZ had more false positives and lower sensitivity scores than CN. Higher plasma oxytocin levels were associated with better sensitivity scores for abstract items in CN and fewer false positives for concrete items in individuals with SZ. Findings indicate that endogenous oxytocin levels predict accurate encoding of lower-level socially relevant information in SZ. PMID:25673435

Tudor-SN, a component of stress granules, regulates growth under salt stress by modulating GA20ox3 mRNA levels in Arabidopsis

PubMed Central

Yan, Chunxia; Yan, Zongyun; Wang, Yizheng; Yan, Xiaoyuan; Han, Yuzhen

2014-01-01

The Tudor-SN protein (TSN) is universally expressed and highly conserved in eukaryotes. In Arabidopsis, TSN is reportedly involved in stress adaptation, but the mechanism involved in this adaptation is not understood. Here, we provide evidence that TSN regulates the mRNA levels of GA20ox3, a key enzyme for gibberellin (GA) biosynthesis. The levels of GA20ox3 transcripts decreased in TSN1/TSN2 RNA interference (RNAi) transgenic lines and increased in TSN1 over-expression (OE) transgenic lines. The TSN1 OE lines displayed phenotypes that may be attributed to the overproduction of GA. No obvious defects were observed in the RNAi transgenic lines under normal conditions, but under salt stress conditions these lines displayed slower growth than wild-type (WT) plants. Two mutants of GA20ox3, ga20ox3-1 and -2, also showed slower growth under stress than WT plants. Moreover, a higher accumulation of GA20ox3 transcripts was observed under salt stress. The results of a western blot analysis indicated that higher levels of TSN1 accumulated after salt treatment than under normal conditions. Subcellular localization studies showed that TSN1 was uniformly distributed in the cytoplasm under normal conditions but accumulated in small granules and co-localized with RBP47, a marker protein for stress granules (SGs), in response to salt stress. The results of RNA immunoprecipitation experiments indicated that TSN1 bound GA20ox3 mRNA in vivo. On the basis of these findings, we conclude that TSN is a novel component of plant SGs that regulates growth under salt stress by modulating levels of GA20ox3 mRNA. PMID:25205572

Gibberellic Acid Regulates Chalcone Synthase Gene Transcription in the Corolla of Petunia hybrida 1

PubMed Central

Weiss, David; van Blokland, Rik; Kooter, Jan M.; Mol, Joseph N. M.; van Tunen, Arjen J.

1992-01-01

The pigmentation of Petunia hybrida corollas is regulated by gibberellic acid (GA3). It controls the increase of flavonoid enzyme levels and their corresponding mRNAs. We have used an in vitro culture system for corollas to study the regulatory role of GA3 in the expression of flavonoid genes. By determining steady-state mRNA levels, we show that the accumulation of chalcone synthase (chs) mRNA in young corollas is dependent on the presence of both sucrose and GA3 in the culture medium. Whereas sucrose had a general metabolic effect on gene expression, the stimulatory role of GA3 was specific. Analysis of nascent transcripts in isolated corolla nuclei showed that changes in steady-state chs mRNA levels correlated very well with changes in the transcription rate. We therefore conclude that GA3 controls the expression of chs at the transcriptional level. Preculturing the corollas in sucrose medium without GA3 resulted in a lower chs mRNA level. The expression could be reinduced by the addition of GA3. The hormone is thus required for the induction but also for the maintenance of chs transcription. The delayed reinduction of chs expression, the lag time in the kinetics of chs mRNA accumulation, and the inhibitory effect of cycloheximide on the action of GA3 suggest that GA3 controls chs transcription in an indirect manner. Our data support a model in which GA3 induces the production of a regulatory protein such as a receptor or a trans-acting factor that is directly involved in chs transcription. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6 PMID:16668613

Glycated albumin is set lower in relation to plasma glucose levels in patients with Cushing's syndrome.

PubMed

Kitamura, Tetsuhiro; Otsuki, Michio; Tamada, Daisuke; Tabuchi, Yukiko; Mukai, Kosuke; Morita, Shinya; Kasayama, Soji; Shimomura, Iichiro; Koga, Masafumi

2013-09-23

Glycated albumin (GA) is an indicator of glycemic control, which has some specific characters in comparison with HbA1c. Since glucocorticoids (GC) promote protein catabolism including serum albumin, GC excess state would influence GA levels. We therefore investigated GA levels in patients with Cushing's syndrome. We studied 16 patients with Cushing's syndrome (8 patients had diabetes mellitus and the remaining 8 patients were non-diabetic). Thirty-two patients with type 2 diabetes mellitus and 32 non-diabetic subjects matched for age, sex and BMI were used as controls. In the patients with Cushing's syndrome, GA was significantly correlated with HbA1c, but the regression line shifted downwards as compared with the controls. The GA/HbA1c ratio in the patients with Cushing's syndrome was also significantly lower than the controls. HbA1c in the non-diabetic patients with Cushing's syndrome was not different from the non-diabetic controls, whereas GA was significantly lower. In 7 patients with Cushing's syndrome who performed self-monitoring of blood glucose, the measured HbA1c was matched with HbA1c estimated from mean blood glucose, whereas the measured GA was significantly lower than the estimated GA. We clarified that GA is set lower in relation to plasma glucose levels in patients with Cushing's syndrome. Copyright © 2013 Elsevier B.V. All rights reserved.

Enhanced Thermionic Emission and Low 1/f Noise in Exfoliated Graphene/GaN Schottky Barrier Diode.

PubMed

Kumar, Ashutosh; Kashid, Ranjit; Ghosh, Arindam; Kumar, Vikram; Singh, Rajendra

2016-03-01

Temperature-dependent electrical transport characteristics of exfoliated graphene/GaN Schottky diodes are investigated and compared with conventional Ni/GaN Schottky diodes. The ideality factor of graphene/GaN and Ni/GaN diodes are measured to be 1.33 and 1.51, respectively, which is suggestive of comparatively higher thermionic emission current in graphene/GaN diode. The barrier height values for graphene/GaN diode obtained using thermionic emission model and Richardson plots are found to be 0.60 and 0.72 eV, respectively, which are higher than predicted barrier height ∼0.40 eV as per the Schottky-Mott model. The higher barrier height is attributed to hole doping of graphene due to graphene-Au interaction which shifts the Fermi level in graphene by ∼0.3 eV. The magnitude of flicker noise of graphene/GaN Schottky diode increases up to 175 K followed by its decrease at higher temperatures. This indicates that diffusion currents and barrier inhomogeneities dominate the electronic transport at lower and higher temperatures, respectively. The exfoliated graphene/GaN diode is found to have lower level of barrier inhomogeneities than conventional Ni/GaN diode, as well as earlier reported graphene/GaN diode fabricated using chemical vapor deposited graphene. The lesser barrier inhomogeneities in graphene/GaN diode results in lower flicker noise by 2 orders of magnitude as compared to Ni/GaN diode. Enhanced thermionic emission current, lower level of inhomogeneities, and reduced flicker noise suggests that graphene-GaN Schottky diodes may have the underlying trend for replacing metal-GaN Schottky diodes.

A Study of Gibberellin Homeostasis and Cryptochrome-Mediated Blue Light Inhibition of Hypocotyl Elongation1[W][OA

PubMed Central

Zhao, Xiaoying; Yu, Xuhong; Foo, Eloise; Symons, Gregory M.; Lopez, Javier; Bendehakkalu, Krishnaprasad T.; Xiang, Jing; Weller, James L.; Liu, Xuanming; Reid, James B.; Lin, Chentao

2007-01-01

Cryptochromes mediate blue light-dependent photomorphogenic responses, such as inhibition of hypocotyl elongation. To investigate the underlying mechanism, we analyzed a genetic suppressor, scc7-D (suppressors of cry1cry2), which suppressed the long-hypocotyl phenotype of the cry1cry2 (cryptochrome1/cryptochrome2) mutant in a light-dependent but wavelength-independent manner. scc7-D is a gain-of-expression allele of the GA2ox8 gene encoding a gibberellin (GA)-inactivating enzyme, GA 2-oxidase. Although scc7-D is hypersensitive to light, transgenic seedlings expressing GA2ox at a level higher than scc7-D showed a constitutive photomorphogenic phenotype, confirming a general role of GA2ox and GA in the suppression of hypocotyl elongation. Prompted by this result, we investigated blue light regulation of mRNA expression of the GA metabolic and catabolic genes. We demonstrated that cryptochromes are required for the blue light regulation of GA2ox1, GA20ox1, and GA3ox1 expression in transient induction, continuous illumination, and photoperiodic conditions. The kinetics of cryptochrome induction of GA2ox1 expression and cryptochrome suppression of GA20ox1 or GA3ox1 expression correlate with the cryptochrome-dependent transient reduction of GA4 in etiolated wild-type seedlings exposed to blue light. Therefore we propose that in deetiolating seedlings, cryptochromes mediate blue light regulation of GA catabolic/metabolic genes, which affect GA levels and hypocotyl elongation. Surprisingly, no significant change in the GA4 content was detected in the whole shoot samples of the wild-type or cry1cry2 seedlings grown in the dark or continuous blue light, suggesting that cryptochromes may also regulate GA responsiveness and/or trigger cell- or tissue-specific changes of the level of bioactive GAs. PMID:17644628

Endogenous Agmatine Induced by Ischemic Preconditioning Regulates Ischemic Tolerance Following Cerebral Ischemia

PubMed Central

Kim, Jae Hwan; Kim, Jae Young; Jung, Jin Young; Lee, Yong Woo; Lee, Won Taek; Huh, Seung Kon

2017-01-01

Ischemic preconditioning (IP) is one of the most important endogenous mechanisms that protect the cells against ischemia-reperfusion (I/R) injury. However, the exact molecular mechanisms remain unclear. In this study, we showed that changes in the level of agmatine were correlated with ischemic tolerance. Changes in brain edema, infarct volume, level of agmatine, and expression of arginine decarboxylase (ADC) and nitric oxide synthases (NOS; inducible NOS [iNOS] and neural NOS [nNOS]) were analyzed during I/R injury with or without IP in the rat brain. After cerebral ischemia, brain edema and infarct volume were significantly reduced in the IP group. The level of agmatine was increased before and during ischemic injury and remained elevated in the early reperfusion phase in the IP group compared to the experimental control (EC) group. During IP, the level of plasma agmatine was increased in the early phase of IP, but that of liver agmatine was abruptly decreased. However, the level of agmatine was definitely increased in the ipsilateral and contralateral hemisphere of brain during the IP. IP also increased the expression of ADC—the enzyme responsible for the synthesis of endogenous agmatine—before, during, and after ischemic injury. In addition, ischemic injury increased endogenous ADC expression in the EC group. The expression of nNOS was reduced in the I/R injured brain in the IP group. These results suggest that endogenous increased agmatine may be a component of the ischemic tolerance response that is induced by IP. Agmatine may have a pivotal role in endogenous ischemic tolerance. PMID:29302205

Ovary-derived precursor gibberellin A9 is essential for female flower development in cucumber.

PubMed

Pimenta Lange, Maria João; Lange, Theo

2016-12-01

Gibberellins (GAs) are hormones that control many aspects of plant development, including flowering. It is well known that stamen is the source of GAs that regulate male and bisexual flower development. However, little is known about the role of GAs in female flower development. In cucumber, high levels of GA precursors are present in ovaries and high levels of bioactive GA 4 are identified in sepals/petals, reflecting the expression of GA 20-oxidase and 3-oxidase in these organs, respectively. Here, we show that the biologically inactive precursor GA 9 moves from ovaries to sepal/petal tissues where it is converted to the bioactive GA 4 necessary for female flower development. Transient expression of a catabolic GA 2-oxidase from pumpkin in cucumber ovaries decreases GA 9 and GA 4 levels and arrests the development of female flowers, and this can be restored by application of GA 9 to petals thus confirming its function. Given that bioactive GAs can promote sex reversion of female flowers, movement of biologically inactive precursors, instead of the hormone itself, might help to maintain floral organ identity, ensuring fruit and seed production. © 2016. Published by The Company of Biologists Ltd.

Sensitivity of Fermi level position at Ga-polar, N-polar, and nonpolar m-plane GaN surfaces to vacuum and air ambient

NASA Astrophysics Data System (ADS)

Janicki, Łukasz; Ramírez-López, Manolo; Misiewicz, Jan; Cywiński, Grzegorz; Boćkowski, Michał; Muzioł, Grzegorz; Chèze, Caroline; Sawicka, Marta; Skierbiszewski, Czesław; Kudrawiec, Robert

2016-05-01

Ga-polar, N-polar, and nonpolar m-plane GaN UN+ structures have been examined in air and vacuum ambient by contactless electroreflectance (CER). This technique is very sensitive to the surface electric field that varies with the Fermi level position at the surface. For UN+ GaN structures [i.e., GaN (undoped)/GaN (n-type)/substrate], a homogeneous built-in electric field is expected in the undoped GaN layer that is manifested by Franz-Keldysh oscillation (FKO) in CER spectra. A clear change in FKO has been observed in CER spectra for N-polar and nonpolar m-plane structures when changing from air to vacuum ambient. This means that those surfaces are very sensitive to ambient atmosphere. In contrast to that, only a small change in FKO can be seen in the Ga-polar structure. This clearly shows that the ambient sensitivity of the Fermi level position at the GaN surface varies with the crystallographic orientation and is very high for N-polar and nonpolar m-plane surfaces. This feature of the N-polar and nonpolar m-plane surfaces can be very important for GaN-based devices grown on these crystallographic orientations and can be utilized in some of the devices, e.g., sensors.

Chemical trend of acceptor levels of Be, Mg, Zn, and Cd in GaAs, GaP, InP and GaN

NASA Astrophysics Data System (ADS)

Wang, Hao; Chen, An-Ban

2000-03-01

We are investigating the “shallow” acceptor levels in the III-nitride semiconductors theoretically. The k·p Hamiltonians and a model central-cell impurity potential have been used to evaluate the ordering of the ionization energies of impurities Be, Mg, Zn, and Cd in GaN. The impurity potential parameters were obtained from studying the same set of impurities in GaAs. These parameters were then transferred to the calculation for other hosts, leaving only one adjustable screening parameter for each host. This procedure was tested in GaP and InP and remarkably good results were obtained. When applied to GaN, this procedure produced a consistent set of acceptor levels with different k·p Hamiltonians. The calculated ionization energies for Be, Mg, Zn and Cd acceptors in GaN are respectively145, 156, 192, and 312 meV for the zincblende structure, and 229, 250, 320, and 510 meV for the wurtzite structure. These and other results will be discussed.

Aerobic Exercise, Estrogens, and Breast Cancer Risk

DTIC Science & Technology

2011-11-01

on endogenous sex hormone levels, menstrual cycle characteristics, and estrogen metabolism in sedentary, eumenorrheic, healthy premenopausal women...changes in menstrual cycle length, and 4) limited changes in estrogen metabolism. The resulting increases in urinary 2-hydroxyestrone levels and 2...effects of a 16-week, aerobic exercise intervention on endogenous sex hormone levels, menstrual cycle characteristics, and estrogen metabolism of young

Electronic properties of deep-level defects in proton irradiated AlGaAs-GaAs solar cells

NASA Technical Reports Server (NTRS)

Li, S. S.

1981-01-01

Deep level transient spectroscopy and capacitance voltage techniques as well as analysis of the forward current voltage (I-V) characteristics and SEM-EIC data were carried out for proton irradiated GaAs solar cells over a wide range of proton energies and proton fluences. Defect and recombination parameters such as defect energy levels and density, carrier capture cross sections and lifetimes as well as diffusion lengths in the undoped n-GaAs LPE layers were determined. Good correlation between these defect parameters and solar cell performance parameters was obtained for GaAs solar cells irradiated by 200 and 290 KeV protons. It was found that 200 to 290 KeV protons will produce the most defects and damages to the GaAs solar cell structure used. The influence of the low temperature (200 to 400 C) periodic thermal annealing on the deep level defects and the performance of the 200 KeV proton irradiated cells is discussed.

(67/68)Ga-labeling agent that liberates (67/68)Ga-NOTA-methionine by lysosomal proteolysis of parental low molecular weight polypeptides to reduce renal radioactivity levels.

PubMed

Uehara, Tomoya; Rokugawa, Takemi; Kinoshita, Mai; Nemoto, Souki; Fransisco Lazaro, Guerra Gomez; Hanaoka, Hirofumi; Arano, Yasushi

2014-11-19

The renal localization of gallium-67 or gallium-68 ((67/68)Ga)-labeled low molecular weight (LMW) probes such as peptides and antibody fragments constitutes a problem in targeted imaging. Wu et al. previously showed that (67)Ga-labeled S-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bz-NOTA)-conjugated methionine ((67)Ga-NOTA-Met) was rapidly excreted from the kidney in urine following lysosomal proteolysis of the parental (67)Ga-NOTA-Bz-SCN-disulfide-stabilized Fv fragment (Bioconjugate Chem., (1997) 8, 365-369). In the present study, a new (67/68)Ga-labeling reagent for LMW probes that liberates (67/68)Ga-NOTA-Met was designed, synthesized, and evaluated using longer-lived (67)Ga in order to reduce renal radioactivity levels. We employed a methionine-isoleucine (MI) dipeptide bond as the cleavable linkage. The amine residue of MI was coupled with SCN-Bz-NOTA for (67)Ga-labeling, while the carboxylic acid residue of MI was derivatized to maleimide for antibody conjugation in order to synthesize NOTA-MI-Mal. A Fab fragment of the anti-Her2 antibody was thiolated with iminothiolane, and NOTA-MI-Mal was conjugated with the antibody fragment by maleimide-thiol chemistry. The Fab fragment was also conjugated with SCN-Bz-NOTA (NOTA-Fab) for comparison. (67)Ga-NOTA-MI-Fab was obtained at radiochemical yields of over 95% and was stable in murine serum for 24 h. In the biodistribution study using normal mice, (67)Ga-NOTA-MI-Fab registered significantly lower renal radioactivity levels from 1 to 6 h postinjection than those of (67)Ga-NOTA-Fab. An analysis of urine samples obtained 6 h after the injection of (67)Ga-NOTA-MI-Fab showed that the majority of radioactivity was excreted as (67)Ga-NOTA-Met. In the biodistribution study using tumor-bearing mice, the tumor to kidney ratios of (67)Ga-NOTA-MI-Fab were 4 times higher (6 h postinjection) than those of (67)Ga-NOTA-Fab. Although further studies including the structure of radiometabolites and/or cleavable linkages are required, the results of the present study indicate that the current chemical design is applicable to the development of (67)Ga-labeled Fabs for low renal radioactivity levels.

Cystathionine γ-Lyase-Produced Hydrogen Sulfide Controls Endothelial NO Bioavailability and Blood Pressure.

PubMed

Szijártó, István András; Markó, Lajos; Filipovic, Milos R; Miljkovic, Jan Lj; Tabeling, Christoph; Tsvetkov, Dmitry; Wang, Ning; Rabelo, Luiza A; Witzenrath, Martin; Diedrich, André; Tank, Jens; Akahoshi, Noriyuki; Kamata, Shotaro; Ishii, Isao; Gollasch, Maik

2018-06-01

Hydrogen sulfide (H 2 S) and NO are important gasotransmitters, but how endogenous H 2 S affects the circulatory system has remained incompletely understood. Here, we show that CTH or CSE (cystathionine γ-lyase)-produced H 2 S scavenges vascular NO and controls its endogenous levels in peripheral arteries, which contribute to blood pressure regulation. Furthermore, eNOS (endothelial NO synthase) and phospho-eNOS protein levels were unaffected, but levels of nitroxyl were low in CTH-deficient arteries, demonstrating reduced direct chemical interaction between H 2 S and NO. Pretreatment of arterial rings from CTH-deficient mice with exogenous H 2 S donor rescued the endothelial vasorelaxant response and decreased tissue NO levels. Our discovery that CTH-produced H 2 S inhibits endogenous endothelial NO bioavailability and vascular tone is novel and fundamentally important for understanding how regulation of vascular tone is tailored for endogenous H 2 S to contribute to systemic blood pressure function. © 2018 American Heart Association, Inc.

Comprehensive Transcriptome Analysis of Phytohormone Biosynthesis and Signaling Genes in the Flowers of Chinese Chinquapin (Castanea henryi).

PubMed

Fan, Xiaoming; Yuan, Deyi; Tian, Xiaoming; Zhu, Zhoujun; Liu, Meilan; Cao, Heping

2017-11-29

Chinese chinquapin (Castanea henryi) nut provides a rich source of starch and nutrients as food and feed, but its yield is restricted by a low ratio of female to male flowers. Little is known about the developmental programs underlying sex differentiation of the flowers. To investigate the involvement of phytohormones during sex differentiation, we described the morphology of male and female floral organs and the cytology of flower sex differentiation, analyzed endogenous levels of indole-3-acetic acid (IAA), gibberellins (GAs), cytokinins (CKs), and abscisic acid (ABA) in the flowers, investigated the effects of exogenous hormones on flower development, and evaluated the expression profiles of genes related to biosyntheses and signaling pathways of these four hormones using RNA-Seq combined with qPCR. Morphological results showed that the flowers consisted of unisexual and bisexual catkins, and could be divided into four developmental stages. HPLC results showed that CK accumulated much more in the female flowers than that in the male flowers, GA and ABA showed the opposite results, while IAA did not show a tendency. The effects of exogenous hormones on sex differentiation were consistent with those of endogenous hormones. RNA-Seq combined with qPCR analyses suggest that several genes may play key roles in hormone biosynthesis and sex differentiation. This study presents the first comprehensive report of phytohormone biosynthesis and signaling during sex differentiation of C. henryi, which should provide a foundation for further mechanistic studies of sex differentiation in Castanea Miller species and other nonmodel plants.

Study of sulfur bonding on gallium arsenide (100) surfaces using supercritical fluid extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cabauy, P.; Darici, Y.; Furton, K.G.

1995-12-01

In the last decades Gallium Arsenide (GaAs) has been considered the semiconductor that will replace silicon because of its direct band gap and high electron mobility. Problems with GaAs Fermi level pinning has halted its widespread use in the electronics industry. The formation of oxides on GaAs results in a high density of surface states that effectively pin the surface Fermi level at the midgap. Studies on sulfur passivation have eliminated oxidation and virtually unpinned the Fermi level on the GaAs surface. This has given rise to interest in sulfur-GaAs bonds. In this presentation, we will discuss the types ofmore » sulfur bonds extracted from a sulfur passivated GaAs (100) using Supercritical Fluid (CO2) Extraction (SFE). SFE can be a valuable tool in the study of chemical speciations on semiconductor surfaces. The variables evaluated to effectively study the sulfur species from the GaAs surface include passivation techniques, supercritical fluid temperatures, densities, and extraction times.« less

Copper-related defects in In0.53Ga0.47As grown by liquid-phase epitaxy

NASA Astrophysics Data System (ADS)

Tilly, L. P.; Grimmeiss, H. G.; Hansson, P. O.

1993-01-01

High-purity In0.53Ga0.47As lattice matched to InP was grown by liquid-phase epitaxy and used for the study of Cu-related defects. The samples had a free-electron carrier concentration of n=5.0×1014 cm-3 and an electron mobility of μ77 K=44 000 cm2/V s. A Cu-related acceptor level 25 meV above the valence-band edge was identified using photoluminescence measurements. Comparing the energy position of this shallow acceptor level with the Ev+157.8-meV Cu-acceptor level in GaAs supports the assumption of an internal energy reference level [J. M. Langer, C. Delerue, M. Lannoo, and H. Heinrich, Phys. Rev. B 38, 7723 (1988)] common to GaAs and InxGa1-xAs.

The ratio of glycated albumin to hemoglobin A1c measured in IFCC units accurately represents the glycation gap.

PubMed

Akatsuka, Junya; Mochizuki, Mie; Musha, Ikuma; Ohtake, Akira; Kobayashi, Kisho; Kikuchi, Toru; Kikuchi, Nobuyuki; Kawamura, Tomoyuki; Urakami, Tatsuhiko; Sugihara, Shigetaka; Hoshino, Tadao; Amemiya, Shin

2015-01-01

The glycation gap (G-gap: difference between measured hemoglobin A1c [A1C] and the value predicted by its regression on the fructosamine level) is stable and associated with diabetic complications. Measuring A1C level in International Federation of Clinical Chemistry (IFCC) units (A1C-SI; mmol/mol) and National Glycohemoglobin Standardization Program units (A1C-NGSP; %) and using glycated albumin (GA) level instead of fructosamine level for calculating the G-gap, we investigated whether the G-gap is better represented by GA/A1C ratio if expressed in SI units (GA/A1C-SI ratio) rather than in NGSP units (GA/A1C-% ratio). We examined 749 Japanese children with type 1 diabetes using simultaneous GA and A1C measurements. Of these, 369 patients were examined more than five times to assess the consistency of the G-gap and the GA/A1C ratio within individuals. The relationship of GA/A1C-% ratio to the corresponding A1C-NGSP was stronger than that of GA/A1C-SI ratio to A1C-IFCC. At enrollment, the inverse relationship between the GA/A1C-SI ratio and G-gap was highly significant (R(2) = 0.95) compared with that between the GA/A1C-% ratio and G-gap (R(2) = 0.69). A highly significant inverse relationship was also observed between the mean GA/A1C-SI ratio and the mean G-gaps obtained individually over time (R(2) = 0.95) compared with that using the corresponding A1C-NGSP (R(2) = 0.67). We conclude that the G-gap is better represented by the GA/A1C-SI ratio. We propose the use of mean GA/A1C-SI ratios easily obtained individually over time as reference values in Japanese children with type 1 diabetes (6.75 ± 0.60 [means ± SD]).

Photoluminescence and capacitance voltage characterization of GaAs surface passivated by an ultrathin GaN interface control layer

NASA Astrophysics Data System (ADS)

Anantathanasarn, Sanguan; Hasegawa, Hideki

2002-05-01

A novel surface passivation technique for GaAs using an ultrathin GaN interface control layer (GaN ICL) formed by surface nitridation was characterized by ultrahigh vacuum (UHV) photoluminescence (PL) and capacitance-voltage ( C- V) measurements. The PL quantum efficiency was dramatically enhanced after being passivated by the GaN ICL structure, reaching as high as 30 times of the initial clean GaAs surface. Further analysis of PL data was done by the PL surface state spectroscopy (PLS 3) simulation technique. PL and C- V results are in good agreement indicating that ultrathin GaN ICL reduces the gap states and unpins the Fermi level, realizing a wide movement of Fermi level within the midgap region and reduction of the effective surface recombination velocity by a factor of 1/60. GaN layer also introduced a large negative surface fixed charge of about 10 12 cm -2. A further improvement took place by depositing a Si 3N 4 layer on GaN ICL/GaAs structure.

Oxalate absorption and endogenous oxalate synthesis from ascorbate in calcium oxalate stone formers and non-stone formers.

PubMed

Chai, Weiwen; Liebman, Michael; Kynast-Gales, Susan; Massey, Linda

2004-12-01

Increased rates of either oxalate absorption or endogenous oxalate synthesis can contribute to hyperoxaluria, a primary risk factor for the formation of calcium oxalate-containing kidney stones. This study involves a comparative assessment of oxalate absorption and endogenous oxalate synthesis in subpopulations of stone formers (SFs) and non-stone formers (NSFs) and an assessment of the effect of ascorbate supplementation on oxalate absorption and endogenous oxalate synthesis. Twenty-nine individuals with a history of calcium oxalate kidney stones (19 men, 10 women) and 19 age-matched NSFs (8 men, 11 women) participated in two 6-day controlled feeding experimental periods: ascorbate-supplement (2 g/d) and no-supplement treatments. An oxalate load consisting of 118 mg of unlabeled oxalate and 18 mg of 13C2 -oxalic acid was administered the morning of day 6 of each experimental period. Mean 13C2 -oxalic acid absorption averaged across the ascorbate and no-supplement treatments was significantly greater in SFs (9.9%) than NSFs (8.0%). SFs also had significantly greater 24-hour post-oxalate load urinary total oxalate and endogenous oxalate levels with both treatments. Twenty-four-hour urinary total oxalate level correlated strongly with both 13C2 -oxalic acid absorption (SFs, r = 0.76; P < 0.01; NSFs, r = 0.62; P < 0.01) and endogenous oxalate synthesis (SFs, r = 0.95; P < 0.01; NSFs, r = 0.92; P < 0.01). SFs are characterized by greater rates of both oxalate absorption and endogenous oxalate synthesis, and both these factors contribute to the hyperoxaluric state. The finding that ascorbate supplementation increased urinary total and endogenous oxalate levels suggested that this practice is a risk factor for individuals predisposed to kidney stones.

ASSAYS FOR ENDOGENOUS COMPONENTS OF HUMAN MILK: COMPARISON OF FRESH AND FROZEN SAMPLES AND CORRESPONDING ANALYTES IN SERUM

EPA Science Inventory

Breast milk is a primary source of nutrition that contains many endogenous compounds that may affect infant development. The goals of this study were to develop reliable assays for selected endogenous breast milk components and to compare levels of those in milk and serum collect...

Symptomless endophytic fungi suppress endogenous levels of salicylic acid and interact with the jasmonate-dependent indirect defense traits of their host, lima bean (Phaseolus lunatus).

PubMed

Navarro-Meléndez, Ariana L; Heil, Martin

2014-07-01

Symptomless ‘type II’ fungal endophytes colonize their plant host horizontally and exert diverse effects on its resistance phenotype. Here, we used wild Lima bean (Phaseolus lunatus) plants that were experimentally colonized with one of three strains of natural endophytes (Bartalinia pondoensis, Fusarium sp., or Cochliobolus lunatus) to investigate the effects of fungal colonization on the endogenous levels of salicylic acid (SA) and jasmonic acid (JA) and on two JA-dependent indirect defense traits. Colonization with Fusarium sp. enhanced JA levels in intact leaves, whereas B. pondoensis suppressed the induction of endogenous JA in mechanically damaged leaves. Endogenous SA levels in intact leaves were significantly decreased by all strains and B. pondoensis and Fusarium sp. decreased SA levels after mechanical damage. Colonization with Fusarium sp. or C. lunatus enhanced the number of detectable volatile organic compounds (VOCs) emitted from intact leaves, and all three strains enhanced the relative amount of several VOCs emitted from intact leaves as well as the number of detectable VOCs emitted from slightly damaged leaves. All three strains completely suppressed the induced secretion of extrafloral nectar (EFN) after the exogenous application of JA. Symptomless endophytes interact in complex and strain-specific ways with the endogenous levels of SA and JA and with the defense traits that are controlled by these hormones. These interactions can occur both upstream and downstream of the defense hormones.

Angular dependent XPS study of surface band bending on Ga-polar n-GaN

NASA Astrophysics Data System (ADS)

Huang, Rong; Liu, Tong; Zhao, Yanfei; Zhu, Yafeng; Huang, Zengli; Li, Fangsen; Liu, Jianping; Zhang, Liqun; Zhang, Shuming; Dingsun, An; Yang, Hui

2018-05-01

Surface band bending and composition of Ga-polar n-GaN with different surface treatments were characterized by using angular dependent X-ray photoelectron spectroscopy. Upward surface band bending of varying degree was observed distinctly upon to the treatment methods. Besides the nitrogen vacancies, we found that surface states of oxygen-containing absorbates (O-H component) also contribute to the surface band bending, which lead the Fermi level pined at a level further closer to the conduction band edge on n-GaN surface. The n-GaN surface with lower surface band bending exhibits better linear electrical properties for Ti/GaN Ohmic contacts. Moreover, the density of positively charged surface states could be derived from the values of surface band bending.

Zn-dopant dependent defect evolution in GaN nanowires

NASA Astrophysics Data System (ADS)

Yang, Bing; Liu, Baodan; Wang, Yujia; Zhuang, Hao; Liu, Qingyun; Yuan, Fang; Jiang, Xin

2015-10-01

Zn doped GaN nanowires with different doping levels (0, <1 at%, and 3-5 at%) have been synthesized through a chemical vapor deposition (CVD) process. The effect of Zn doping on the defect evolution, including stacking fault, dislocation, twin boundary and phase boundary, has been systematically investigated by transmission electron microscopy and first-principles calculations. Undoped GaN nanowires show a hexagonal wurtzite (WZ) structure with good crystallinity. Several kinds of twin boundaries, including (101&cmb.macr;3), (101&cmb.macr;1) and (202&cmb.macr;1), as well as Type I stacking faults (...ABABC&cmb.b.line;BCB...), are observed in the nanowires. The increasing Zn doping level (<1 at%) induces the formation of screw dislocations featuring a predominant screw component along the radial direction of the GaN nanowires. At high Zn doping level (3-5 at%), meta-stable cubic zinc blende (ZB) domains are generated in the WZ GaN nanowires. The WZ/ZB phase boundary (...ABABAC&cmb.b.line;BA...) can be identified as Type II stacking faults. The density of stacking faults (both Type I and Type II) increases with increasing the Zn doping levels, which in turn leads to a rough-surface morphology in the GaN nanowires. First-principles calculations reveal that Zn doping will reduce the formation energy of both Type I and Type II stacking faults, favoring their nucleation in GaN nanowires. An understanding of the effect of Zn doping on the defect evolution provides an important method to control the microstructure and the electrical properties of p-type GaN nanowires.Zn doped GaN nanowires with different doping levels (0, <1 at%, and 3-5 at%) have been synthesized through a chemical vapor deposition (CVD) process. The effect of Zn doping on the defect evolution, including stacking fault, dislocation, twin boundary and phase boundary, has been systematically investigated by transmission electron microscopy and first-principles calculations. Undoped GaN nanowires show a hexagonal wurtzite (WZ) structure with good crystallinity. Several kinds of twin boundaries, including (101&cmb.macr;3), (101&cmb.macr;1) and (202&cmb.macr;1), as well as Type I stacking faults (...ABABC&cmb.b.line;BCB...), are observed in the nanowires. The increasing Zn doping level (<1 at%) induces the formation of screw dislocations featuring a predominant screw component along the radial direction of the GaN nanowires. At high Zn doping level (3-5 at%), meta-stable cubic zinc blende (ZB) domains are generated in the WZ GaN nanowires. The WZ/ZB phase boundary (...ABABAC&cmb.b.line;BA...) can be identified as Type II stacking faults. The density of stacking faults (both Type I and Type II) increases with increasing the Zn doping levels, which in turn leads to a rough-surface morphology in the GaN nanowires. First-principles calculations reveal that Zn doping will reduce the formation energy of both Type I and Type II stacking faults, favoring their nucleation in GaN nanowires. An understanding of the effect of Zn doping on the defect evolution provides an important method to control the microstructure and the electrical properties of p-type GaN nanowires. Electronic supplementary information (ESI) available: HRTEM image of undoped GaN nanowires and first-principles calculations of Zn doped WZ-GaN. See DOI: 10.1039/c5nr04771d

Valence-band structure of the ferromagnetic semiconductor GaMnAs studied by spin-dependent resonant tunneling spectroscopy.

PubMed

Ohya, Shinobu; Muneta, Iriya; Hai, Pham Nam; Tanaka, Masaaki

2010-04-23

The valence-band structure and the Fermi level (E(F)) position of ferromagnetic-semiconductor GaMnAs are quantitatively investigated by electrically detecting the resonant tunneling levels of a GaMnAs quantum well (QW) in double-barrier heterostructures. The resonant level from the heavy-hole first state is clearly observed in the metallic GaMnAs QW, indicating that holes have a high coherency and that E(F) exists in the band gap. Clear enhancement of tunnel magnetoresistance induced by resonant tunneling is demonstrated in these double-barrier heterostructures.

Gibberellin Application at Pre-Bloom in Grapevines Down-Regulates the Expressions of VvIAA9 and VvARF7, Negative Regulators of Fruit Set Initiation, during Parthenocarpic Fruit Development

PubMed Central

Jung, Chan Jin; Hur, Youn Young; Yu, Hee-Ju; Noh, Jung-Ho; Park, Kyo-Sun; Lee, Hee Jae

2014-01-01

Fruit set is initiated only after fertilization and is tightly regulated primarily by gibberellins (GAs) and auxins. The application of either of these hormones induces parthenocarpy, fruit set without fertilization, but the molecular mechanism underlying this induction is poorly understood. In the present study, we have shown that the parthenocarpic fruits induced by GA application at pre-bloom result from the interaction of GA with auxin signaling. The transcriptional levels of the putative negative regulators of fruit set initiation, including Vitis auxin/indole-3-acetic acid transcription factor 9 (VvIAA9), Vitis auxin response factor 7 (VvARF7), and VvARF8 were monitored during inflorescence development in seeded diploid ‘Tamnara’ grapevines with or without GA application. Without GA application, VvIAA9, VvARF7, and VvARF8 were expressed at a relatively high level before full bloom, but decreased thereafter following pollination. After GA application at 14 days before full bloom (DBF); however, the expression levels of VvIAA9 and VvARF7 declined at 5 DBF prior to pollination. The effects of GA application on auxin levels or auxin signaling were also analyzed by monitoring the expression patterns of auxin biosynthesis genes and auxin-responsive genes with or without GA application. Transcription levels of the auxin biosynthesis genes Vitis anthranilate synthase β subunit (VvASB1-like), Vitis YUCCA2 (VvYUC2), and VvYUC6 were not significantly changed by GA application. However, the expressions of Vitis Gretchen Hagen3.2 (VvGH3.2) and VvGH3.3, auxin-responsive genes, were up-regulated from 2 DBF to full bloom with GA application. Furthermore, the Vitis GA signaling gene, VvDELLA was up-regulated by GA application during 12 DBF to 7 DBF, prior to down-regulation of VvIAA9 and VvARF7. These results suggest that VvIAA9 and VvARF7 are negative regulators of fruit set initiation in grapevines, and GA signaling is integrated with auxin signaling via VvDELLA during parthenocarpic fruit development in grapevines. PMID:24743886

Gibberellin application at pre-bloom in grapevines down-regulates the expressions of VvIAA9 and VvARF7, negative regulators of fruit set initiation, during parthenocarpic fruit development.

PubMed

Jung, Chan Jin; Hur, Youn Young; Yu, Hee-Ju; Noh, Jung-Ho; Park, Kyo-Sun; Lee, Hee Jae

2014-01-01

Fruit set is initiated only after fertilization and is tightly regulated primarily by gibberellins (GAs) and auxins. The application of either of these hormones induces parthenocarpy, fruit set without fertilization, but the molecular mechanism underlying this induction is poorly understood. In the present study, we have shown that the parthenocarpic fruits induced by GA application at pre-bloom result from the interaction of GA with auxin signaling. The transcriptional levels of the putative negative regulators of fruit set initiation, including Vitis auxin/indole-3-acetic acid transcription factor 9 (VvIAA9), Vitis auxin response factor 7 (VvARF7), and VvARF8 were monitored during inflorescence development in seeded diploid 'Tamnara' grapevines with or without GA application. Without GA application, VvIAA9, VvARF7, and VvARF8 were expressed at a relatively high level before full bloom, but decreased thereafter following pollination. After GA application at 14 days before full bloom (DBF); however, the expression levels of VvIAA9 and VvARF7 declined at 5 DBF prior to pollination. The effects of GA application on auxin levels or auxin signaling were also analyzed by monitoring the expression patterns of auxin biosynthesis genes and auxin-responsive genes with or without GA application. Transcription levels of the auxin biosynthesis genes Vitis anthranilate synthase β subunit (VvASB1-like), Vitis YUCCA2 (VvYUC2), and VvYUC6 were not significantly changed by GA application. However, the expressions of Vitis Gretchen Hagen3.2 (VvGH3.2) and VvGH3.3, auxin-responsive genes, were up-regulated from 2 DBF to full bloom with GA application. Furthermore, the Vitis GA signaling gene, VvDELLA was up-regulated by GA application during 12 DBF to 7 DBF, prior to down-regulation of VvIAA9 and VvARF7. These results suggest that VvIAA9 and VvARF7 are negative regulators of fruit set initiation in grapevines, and GA signaling is integrated with auxin signaling via VvDELLA during parthenocarpic fruit development in grapevines.

Comparison of annual variability in HbA1c and glycated albumin in patients with type 1 vs. type 2 diabetes mellitus.

PubMed

Koga, Masafumi; Murai, Jun; Morita, Shinya; Saito, Hiroshi; Kasayama, Soji

2013-01-01

It has been suggested that plasma glucose (PG) levels per se and long-term variations in PG levels are associated with diabetic vascular complications. Glycated albumin (GA) reflects shorter-term glycemic control, as well as postprandial PG levels, as compared to HbA1c. In this study, we hypothesized that GA more strongly reflects long-term variations in PG levels than HbA1c, and compared the variability of HbA1c and that of GA in patients with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). This study included 8 T1DM patients and 48 T2DM patients. Over a 1-year period, HbA1c and GA were measured every month and the mean values and coefficients of variation (CV) for each patient were calculated. In both T1DM and T2DM patients, the CV of GA was significantly higher than the CV of HbA1c. Both the CV of HbA1c and the CV of GA were significantly higher in the T1DM patients than in the T2DM patients. The annual variability in GA was greater than that in HbA1c. In addition, the annual variability in HbA1c and that in GA in the T1DM patients were greater than in the T2DM patients. Our findings suggest that GA more accurately reflects long-term variations in PG levels than HbA1c. Copyright © 2013 Elsevier Inc. All rights reserved.

The Ratio of Estimated Average Glucose to Fasting Plasma Glucose Level Is Superior to Glycated Albumin, Hemoglobin A1c, Fructosamine, and GA/A1c Ratio for Assessing β-Cell Function in Childhood Diabetes

PubMed Central

Lee, Ji Eun; Lee, Ji Woo; Fujii, Tatsuyoshi; Fujii, Noriyoshi; Choi, Jong Weon

2014-01-01

Objective. This study investigated the use of the estimated average glucose to fasting plasma glucose ratio (eAG/fPG ratio) to screen for β-cell function in pediatric diabetes. Methods. Glycated hemoglobin (HbA1c), glycated albumin (GA), fructosamine, insulin, and C-peptide levels were measured. The ratio of GA to HbA1c (GA/A1c ratio) was calculated, and the homeostasis model assessment of β-cell function (HOMA-β) was determined. Results. Median values of C-peptide, insulin, and HOMA-β levels were significantly higher in patients with an increased eAG/fPG ratio than in those with a decreased eAG/fPG ratio. C-peptide and HOMA-β levels were more closely correlated with the eAG/fPG ratio than with GA, HbA1c, the GA/A1c ratio, and fructosamine. In contrast, body mass index was significantly associated with GA, GA/A1c ratio, and fructosamine, but not with the eAG/fPG ratio and HbA1c levels. To test the diagnostic accuracies of the eAG/fPG ratio for identifying HOMA-β > 30.0% in patients with type 2 diabetes, the area under the ROC curve of the eAG/fPG ratio was significantly larger than that of the GA/A1c ratio [0.877 (95% CI, 0.780–0.942) versus 0.775 (95% CI, 0.664–0.865), P = 0.039]. Conclusions. A measurement of the eAG/fPG ratio may provide helpful information for assessing β-cell function in pediatric patients with diabetes. PMID:25013775

Improved InGaN/GaN light-emitting diodes with a p-GaN/n-GaN/p-GaN/n-GaN/p-GaN current-spreading layer.

PubMed

Zhang, Zi-Hui; Tan, Swee Tiam; Liu, Wei; Ju, Zhengang; Zheng, Ke; Kyaw, Zabu; Ji, Yun; Hasanov, Namig; Sun, Xiao Wei; Demir, Hilmi Volkan

2013-02-25

This work reports both experimental and theoretical studies on the InGaN/GaN light-emitting diodes (LEDs) with optical output power and external quantum efficiency (EQE) levels substantially enhanced by incorporating p-GaN/n-GaN/p-GaN/n-GaN/p-GaN (PNPNP-GaN) current spreading layers in p-GaN. Each thin n-GaN layer sandwiched in the PNPNP-GaN structure is completely depleted due to the built-in electric field in the PNPNP-GaN junctions, and the ionized donors in these n-GaN layers serve as the hole spreaders. As a result, the electrical performance of the proposed device is improved and the optical output power and EQE are enhanced.

Glycyrrhizic acid attenuates growth of Leishmania donovani by depleting ergosterol levels.

PubMed

Dinesh, Neeradi; Neelagiri, Soumya; Kumar, Vinay; Singh, Sushma

2017-05-01

In the present study, glycyrrhizic acid (GA) the main component of Glycyrrhiza glabra was evaluated for its efficacy as antileishmanial agent and its mode of action explored. GA inhibits promastigotes and intracellular amastigotes in a dose dependent manner at an IC 50 value of 34 ± 3.0 μM and 20 ± 4.2 μM respectively. GA was non-toxic against THP-1 macrophage host cell line. GA was found to inhibit recombinant Leishmania donovani HMG-CoA reductase (LdHMGR) enzyme at the half-maximum inhibitory concentration of 24 ± 4.3 μM indicating the sensitivity and specificity of GA towards the enzyme. However, GA could cause only 30% reduction in HMGR activity when measured in Leishmania promastigotes treated with 34 μM of GA. Interestingly western blot analysis revealed fivefold reduced HMGR expression in GLA treated promastigotes. To further study the mode of action of GA, we used transgenic parasites overexpressing LdHMGR. Results indicated that ∼2 fold resistance was exhibited by LdHMGR overexpressing promastigotes to GA with an IC 50 value of 74 μM compared to the wild type parasite. This explained the specific binding of GA to LdHMGR enzyme. There was ∼2 fold depletion in ergosterol levels in wild type promastigotes compared to the HMGR overexpressors. This data was further validated by exogenous supplementation of GA treated cells with ergosterol and 40% reversal of growth inhibition was observed. The results obtained suggested that GA kills the parasite by affecting sterol biosynthetic pathway, especially by inhibiting the L. donovani HMGR and altering ergosterol levels. The finding from the current study shows that GA is a potential antileishmanial chemotherapeutic agent. Copyright © 2017 Elsevier Inc. All rights reserved.

Gibberellin DELLA signaling targets the retromer complex to redirect protein trafficking to the plasma membrane

PubMed Central

Salanenka, Yuliya; Verstraeten, Inge; Löfke, Christian; Tabata, Kaori; Naramoto, Satoshi; Glanc, Matouš; Friml, Jiří

2018-01-01

The plant hormone gibberellic acid (GA) is a crucial regulator of growth and development. The main paradigm of GA signaling puts forward transcriptional regulation via the degradation of DELLA transcriptional repressors. GA has also been shown to regulate tropic responses by modulation of the plasma membrane incidence of PIN auxin transporters by an unclear mechanism. Here we uncovered the cellular and molecular mechanisms by which GA redirects protein trafficking and thus regulates cell surface functionality. Photoconvertible reporters revealed that GA balances the protein traffic between the vacuole degradation route and recycling back to the cell surface. Low GA levels promote vacuolar delivery and degradation of multiple cargos, including PIN proteins, whereas high GA levels promote their recycling to the plasma membrane. This GA effect requires components of the retromer complex, such as Sorting Nexin 1 (SNX1) and its interacting, microtubule (MT)-associated protein, the Cytoplasmic Linker-Associated Protein (CLASP1). Accordingly, GA regulates the subcellular distribution of SNX1 and CLASP1, and the intact MT cytoskeleton is essential for the GA effect on trafficking. This GA cellular action occurs through DELLA proteins that regulate the MT and retromer presumably via their interaction partners Prefoldins (PFDs). Our study identified a branching of the GA signaling pathway at the level of DELLA proteins, which, in parallel to regulating transcription, also target by a nontranscriptional mechanism the retromer complex acting at the intersection of the degradation and recycling trafficking routes. By this mechanism, GA can redirect receptors and transporters to the cell surface, thus coregulating multiple processes, including PIN-dependent auxin fluxes during tropic responses. PMID:29463731

Geranyl acetate esterase controls and regulates the level of geraniol in lemongrass (Cymbopogon flexuosus Nees ex Steud.) mutant cv. GRL-1 leaves.

PubMed

Ganjewala, Deepak; Luthra, Rajesh

2009-01-01

Essential oil isolated from lemongrass (Cymbopogon flexuosus) mutant cv. GRL-1 leaves is mainly composed of geraniol (G) and geranyl acetate (GA). The proportion of G and GA markedly fluctuates during leaf development. The proportions of GA and G in the essential oil recorded at day 10 after leaf emergence were approximately 59% and approximately 33% respectively. However, the level of GA went down from approximately 59 to approximately 3% whereas the level of G rose from approximately 33 to approximately 91% during the leaf growth period from day 10 to day 50. However, the decline in the level of GA was most pronounced in the early (day 10 to day 30) stage of leaf growth. The trend of changes in the proportion of GA and G has clearly indicated the role of an esterase that must be involved in the conversion of GA to G during leaf development. We isolated an esterase from leaves of different ages that converts GA into G and has been given the name geranyl acetate esterase (GAE). The GAE activity markedly varied during the leaf development cycle; it was closely correlated with the monoterpene (GA and G) composition throughout leaf development. GAE appeared as several isoenzymes but only three (GAE-I, GAE-II, and GAE-III) of them had significant GA cleaving activity. The GAE isoenzymes pattern was greatly influenced by the leaf developmental stages and so their GA cleaving activities. Like the GAE activity, GAE isoenzyme patterns were also found to be consistent with the monoterpene (GA and G) composition. GAE had an optimum pH at 8.5 and temperature at 30 degrees C. Besides GAE, a compound with phosphatase activity capable of hydrolyzing geranyl diphosphate (GPP) to produce geraniol has also been isolated.

The effects of DELLAs on growth change with developmental stage and brassinosteroid levels.

PubMed

Stewart Lilley, Jodi L; Gan, Yinbo; Graham, Ian A; Nemhauser, Jennifer L

2013-10-01

There are two stages in photomorphogenesis. First, seedlings detect light and open their cotyledons. Second, seedlings optimize their light environment by controlled elongation of the seedling stem or hypocotyl. In this study, we used time-lapse imaging to investigate the relationship between the brassinosteroid (BR) and gibberellin (GA) hormones across both stages of photomorphogenesis. During the transition between one stage and the other, growth promotion by BRs and GAs switched from an additive to a synergistic relationship. Molecular genetic analysis revealed unexpected roles for known participants in the GA pathway during this period. Members of the DELLA family could either repress or enhance BR growth responses, depending on developmental stage. At the transition point for seedling growth dynamics, the BR and GA pathways had opposite effects on DELLA protein levels. In contrast to GA-induced DELLA degradation, BR treatments increased the levels of REPRESSOR of ga1-3 (RGA) and mimicked the molecular effects of stabilizing DELLAs. In addition, DELLAs showed complex regulation of genes involved in BR biosynthesis, implicating them in BR homeostasis. Growth promotion by GA alone depended on the PHYTOCHROME INTERACTING FACTOR (PIF) family of master growth regulators. The effects of BR, including the synergistic effects with GA, were largely independent of PIFs. These results point to a multi-level, dynamic relationship between the BR and GA pathways. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

GaAsSb bandgap, surface fermi level, and surface state density studied by photoreflectance modulation spectroscopy

NASA Astrophysics Data System (ADS)

Hwang, J. S.; Tsai, J. T.; Su, I. C.; Lin, H. C.; Lu, Y. T.; Chiu, P. C.; Chyi, J. I.

2012-05-01

The bandgap, surface Fermi level, and surface state density of a series of GaAs1-xSbx surface intrinsic-n+ structures with GaAs as substrate are determined for various Sb mole fractions x by the photoreflectance modulation spectroscopy. The dependence of the bandgap on the mole composition x is in good agreement with previous measurements as well as predictions calculated using the dielectric model of Van Vechten and Bergstresser in Phys. Rev. B 1, 3551 (1970). For a particular composition x, the surface Fermi level is always strongly pinned within the bandgap of GaAs1-xSbx and we find its variation with composition x is well described by a function EF = 0.70 - 0.192 x for 0 ≦ x ≦ 0.35, a result which is notably different from that reported by Chouaib et al. [Appl. Phys. Lett. 93, 041913 (2008)]. Our results suggest that the surface Fermi level is pinned at the midgap of GaAs and near the valence band of the GaSb.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Shiyan; Mei, Dajiang, E-mail: meidajiang718@pku.edu.cn; Du, Xin

Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} solutions with high Si doping level (x=1/2) are considered and new compound AgGaSiSe{sub 4} has been synthesized. It crystallizes in space group Aea2 and possesses very long axis of a=63.06(1)Å. The three-dimensional framework in AgGaSiSe{sub 4} is composed of AgSe{sub 3} trigonal planar units, AgSe{sub 4} tetrahedra and MSe{sub 4}(M=Si, Ga) tetrahedra. AgGaSiSe{sub 4} is a congruently melting compound with the melt temperature of 759 °C. The diffuse reflectance measurements reveal the band gap of 2.63 eV in AgGaSiSe{sub 4} and the value is 0.33 eV larger than that of Ag{sub 3}Ga{sub 3}SiSe{sub 8} (2.30more » eV). - Graphical abstract: The Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} with high Si doping level (x=1/2) has been studied and the new compound AgGaSiSe{sub 4} was synthesized for the first time. AgGaSiSe{sub 4} crystallizes in a new structure type in space group Aea2 and adopts a three-dimensional framework consisting of AgSe{sub 3} trigonal planar units, AgSe{sub 4} tetrahedra and MSe{sub 4} (M=Si, Ge) tetrahedra. Display Omitted - Highlights: • Study of Ag{sub 1−x}Ga{sub 1−x}Si{sub x}Se{sub 2} with high Si doping level (x=1/2). • Successful synthesis of new compound named AgGaSiSe{sub 4}. • AgGaSiSe{sub 4} crystallizes in space group Aea2 and adopts a three-dimensional framework. • The energy band gap of AgGaSiSe{sub 4} is enlarged compared with Ag{sub 3}Ga{sub 3}SiSe{sub 8}.« less

Uniconazole-induced starch accumulation in the bioenergy crop duckweed (Landoltia punctata) I: transcriptome analysis of the effects of uniconazole on chlorophyll and endogenous hormone biosynthesis.

PubMed

Liu, Yang; Fang, Yang; Huang, Mengjun; Jin, Yanling; Sun, Jiaolong; Tao, Xiang; Zhang, Guohua; He, Kaize; Zhao, Yun; Zhao, Hai

2015-01-01

Duckweed is a novel aquatic bioenergy crop that is found ubiquitously throughout the world. Uniconazole plays an important role in improving crop production through the regulation of endogenous hormone levels. We found that a high quantity and quality of duckweed growth can be achieved by uniconazole application, although the mechanisms are unknown. The fronds of Landoltia punctata were sprayed evenly with 800 mg/L uniconazole. The dry weight following treatment increased by 10% compared to the controls at 240 h. Endogenous cytokinin (CK) and abscisic acid (ABA) content both increased compared to the control, while the level of gibberellins (GAs) decreased. Additionally, gene expression profiling results showed that the expression of transcripts encoding key enzymes involved in endogenous CK and ABA biosynthesis were up-regulated, while the transcripts of key enzymes for GAs biosynthesis were down-regulated. On the other hand, chlorophyll a and chlorophyll b contents were both increased compared with the control. Moreover, the net photosynthetic rate was elevated to 25.6 μmol CO2/m(2)/s compared with the control value of 22.05 μmol CO2/m(2)/s. Importantly, the expression of some chlorophyll biosynthesis-related transcripts was up-regulated. Uniconazole treatment altered endogenous hormone levels and enhanced chlorophyll content and net photosynthetic rate in duckweed by regulating key enzymes involved in endogenous hormone and chlorophyll biosynthesis. The alterations of endogenous hormones and the increase of chlorophyll and photosynthetic rate data support the increase of biomass and starch accumulation.

Theoretical studies of optical gain tuning by hydrostatic pressure in GaInNAs/GaAs quantum wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gladysiewicz, M.; Wartak, M. S.; Department of Physics and Computer Science, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5

In order to describe theoretically the tuning of the optical gain by hydrostatic pressure in GaInNAs/GaAs quantum wells (QWs), the optical gain calculations within kp approach were developed and applied for N-containing and N-free QWs. The electronic band structure and the optical gain for GaInNAs/GaAs QW were calculated within the 10-band kp model which takes into account the interaction of electron levels in the QW with the nitrogen resonant level in GaInNAs. It has been shown that this interaction increases with the hydrostatic pressure and as a result the optical gain for GaInNAs/GaAs QW decreases by about 40% and 80%more » for transverse electric and transverse magnetic modes, respectively, for the hydrostatic pressure change from 0 to 40 kilobars. Such an effect is not observed for N-free QWs where the dispersion of electron and hole energies remains unchanged with the hydrostatic pressure. This is due to the fact that the conduction and valence band potentials in GaInAs/GaAs QW scale linearly with the hydrostatic pressure.« less

Mindfulness and heart rate variability in individuals with high and low generalized anxiety symptoms.

PubMed

Mankus, Annette M; Aldao, Amelia; Kerns, Caroline; Mayville, Elena Wright; Mennin, Douglas S

2013-07-01

Mindfulness has been incorporated into several treatment approaches for psychopathology. Despite the popularity of this approach, relatively few empirical investigations have examined the relationship between mindfulness and autonomic indicators of flexible emotion regulation, such as heart rate variability (HRV). Generalized anxiety disorder (GAD) has been associated with both low levels of mindfulness and HRV. In this investigation, we examined the relationship between HRV and mindfulness in the context of elevated generalized anxiety (GA) symptoms--an analog for GAD--by examining whether GA level moderated this relationship. HRV was collected while participants completed self-report measures of GA and trait mindfulness. GA level interacted with mindfulness in the prediction of HRV; in the high GA, but not low GA group, mindfulness was positively associated with HRV. This suggests that for individuals with high GA, mindfulness may enhance parasympathetic influences on the heart rate. We address the limitations of the current investigation and suggest avenues for future research on mindfulness-related changes in tonic and phasic HRV over time. Copyright © 2013 Elsevier Ltd. All rights reserved.

Modulation of transferrin receptor mRNA by transferrin-gallium in human myeloid HL60 and lymphoid CCRF-CEM leukaemic cells.

PubMed Central

Ul-Haq, R; Chitambar, C R

1993-01-01

Gallium binds to the iron transport protein transferrin (Tf), is incorporated into cells through transferrin receptors (TfR) and inhibits iron-dependent DNA synthesis. Since cellular TfR expression is tightly regulated by the availability of iron, we investigated the effects of transferrin-gallium (Tf-Ga) on TfR mRNA levels in myeloid HL60 and lymphoid CCRF-CEM cells. In HL60 cells, Tf-Ga increased TfR mRNA levels in a dose-dependent fashion. This increase in TfR mRNA was blocked by Tf-Fe and by cycloheximide. Analysis of the rate of mRNA decay in the presence of actinomycin D revealed that the half-life of TfR mRNA was increased in HL60 cells incubated with Tf-Ga. The rate of transcription of TfR mRNA was not increased by Tf-Ga. In contrast with HL60 cells, CCRF-CEM cells displayed a decrease in the level of TfR mRNA after incubation with Tf-Ga. Tf-Ga inhibited iron uptake in both HL60 and CCRF-CEM cells but increased the level of TfR mRNA only in HL60 cells, suggesting that the Tf-Ga induction of TfR mRNA was not solely due to inhibition of cellular iron uptake. At growth-inhibitory concentrations, Tf-Ga increased the TfR mRNA level in HL60 cells but decreased it in CCRF-CEM cells. Our studies suggest that in HL60 cells, gallium regulates TfR expression at the post-transcriptional level by mechanisms which require de novo protein synthesis and involve interaction with iron. The divergent effects of Tf-Ga on TfR mRNA in myeloid HL60 and lymphoid CCRF-CEM cells suggest that differences exist in the regulation of TfR expression between these two cell types. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 PMID:8379943

Acute myocardial infarction without significant coronary stenoses associated with endogenous subclinical hyperthyroidism.

PubMed

Patanè, Salvatore; Marte, Filippo; Sturiale, Mauro

2012-04-05

Subclinical hyperthyroidism is an increasingly recognized entity that is defined as a normal serum free thyroxine and free triiodothyronine levels with a thyroid-stimulating hormone level suppressed below the normal range and usually undetectable. It has been reported that subclinical hyperthyroidism is not associated with coronary heart disease or mortality from cardiovascular causes but it is sufficient to induce arrhythmias including atrial fibrillation and atrial flutter. Nowadays, there is growing interest regarding endogenous sublinical hyperthyroidism and the cardiovascular system. We present a case of acute myocardial infarction without significant coronary stenoses in a 75-year-old Italian woman with endogenous subclinical hyperthyroidism. Also this case focuses attention on the importance of a correct evaluation of endogenous subclinical hyperthyroidism. Copyright © 2009 Elsevier Ireland Ltd. All rights reserved.

Proteomic Analysis Revealed the Important Role of Vimentin in Human Cervical Carcinoma HeLa Cells Treated With Gambogic Acid*

PubMed Central

Yue, Qingxi; Feng, Lixing; Cao, Biyin; Liu, Miao; Zhang, Dongmei; Wu, Wanying; Jiang, Baohong; Yang, Min; Liu, Xuan; Guo, Dean

2016-01-01

Gambogic acid (GA) is an anticancer agent in phase IIb clinical trial in China. In HeLa cells, GA inhibited cell proliferation, induced cell cycle arrest at G2/M phase and apoptosis, as showed by results of MTT assay and flow cytometric analysis. Possible target-related proteins of GA were searched using comparative proteomic analysis (2-DE) and nine proteins at early (3 h) stage together with nine proteins at late (24 h) stage were found. Vimentin was the only target-related protein found at both early and late stage. Results of both 2-DE analysis and Western blotting assay suggested cleavage of vimentin induced by GA. MS/MS analysis of cleaved vimentin peptides indicated possible cleavage sites of vimentin at or near ser51 and glu425. Results of targeted proteomic analysis showed that GA induced change in phosphorylation state of the vimentin head domain (aa51–64). Caspase inhibitors could not abrogate GA-induced cleavage of vimentin. Over-expression of vimentin ameliorated cytotoxicity of GA in HeLa cells. The GA-activated signal transduction, from p38 MAPK, heat shock protein 27 (HSP27), vimentin, dysfunction of cytoskeleton, to cell death, was predicted and then confirmed. Results of animal study showed that GA treatment inhibited tumor growth in HeLa tumor-bearing mice and cleavage of vimentin could be observed in tumor xenografts of GA-treated animals. Results of immunohistochemical staining also showed down-regulated vimentin level in tumor xenografts of GA-treated animals. Furthermore, compared with cytotoxicity of GA in HeLa cells, cytotoxicity of GA in MCF-7 cells with low level of vimentin was weaker whereas cytotoxicity of GA in MG-63 cells with high level of vimentin was stronger. These results indicated the important role of vimentin in the cytotoxicity of GA. The effects of GA on vimentin and other epithelial-to-mesenchymal transition (EMT) markers provided suggestion for better usage of GA in clinic. PMID:26499837

Endogenous CO monitoring in exhalation with tunable diode lasers: applications to clinical and biomedical diagnostics

NASA Astrophysics Data System (ADS)

Stepanov, Eugene V.; Zyrianov, Pavel V.; Miliaev, Valerii A.; Shulagin, Yurii A.; D'yachenko, Alexander I.

1999-07-01

Middle IR tunable diode lasers were applied to studies of pulmonary excretion of endogenous carbon monoxide (CO). Variations of the CO content level in exhaled air of healthy nonsmokers were investigated for different environmental conditions with the applied laser technique. Correlation of the obtained data with atmospheric CO contamination and elevated oxygen content were studied as well as diurnal variations of the endogenous CO in exhalation was observed. Criteria for correct conditions of the endogenous CO detection in breath could be derive don this basis. Developed laser approach and methods were applied for the analysis of the excreted CO level in different diseases like bronchial asthma, cystic fibrosis, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, anemia and hepatitis. Laser based close-to-real-time monitoring of the endogenous CO elimination with breath in the course of different dynamic tests was demonstrated to be informative in studies of blood oxygen transport and pH variations in tissues for different challenges tests in human physiology.

Material quality frontiers of MOVPE grown AlGaAs for minority carrier devices

NASA Astrophysics Data System (ADS)

Heckelmann, S.; Lackner, D.; Dimroth, F.; Bett, A. W.

2017-04-01

In this study, secondary ion mass spectroscopy of oxygen, deep level transient spectroscopy and power dependent relative photoluminescence are compared regarding their ability to resolve differences in AlxGa1-xAs material quality. AlxGa1-xAs samples grown with two different trimethylaluminum sources showing low and high levels of oxygen contamination are compared. As tested in the growth of minority carrier devices, i.e. AlxGa1-xAs solar cells, the two precursors clearly lead to different device characteristics. It is shown that secondary ion mass spectroscopy could not resolve the difference in oxygen concentration, whereas deep level transient spectroscopy and photoluminescence based measurements indicate the influence of the precursor oxygen level on the material quality.

Electrochemically deposited gallium oxide nanostructures on silicon substrates

PubMed Central

2014-01-01

We report a synthesis of β-Ga2O3 nanostructures on Si substrate by electrochemical deposition using a mixture of Ga2O3, HCl, NH4OH, and H2O. The presence of Ga3+ ions contributed to the deposition of Ga2O3 nanostructures on the Si surface with the assistance of applied potentials. The morphologies of the grown structures strongly depended on the molarity of Ga2O3 and pH level of electrolyte. β-Ga2O3 nanodot-like structures were grown on Si substrate at a condition with low molarity of Ga2O3. However, Ga2O3 nanodot structures covered with nanorods on top of their surfaces were obtained at higher molarity, and the densities of nanorods seem to increase with the decrease of pH level. High concentration of Ga3+ and OH- ions may promote the reaction of each other to produce Ga2O3 nanorods in the electrolyte. Such similar nature of Ga2O3 nanorods was also obtained by using hydrothermal process. The grown structures seem to be interesting for application in electronic and optoelectronic devices as well as to be used as a seed structure for subsequent chemical synthesis of GaN by thermal transformation method. PMID:24629107

Increased carboxyhemoglobin level during liver resection with inflow occlusion.

PubMed

Godai, Kohei; Hasegawa-Moriyama, Maiko; Kuniyoshi, Tamotsu; Matsunaga, Akira; Kanmura, Yuichi

2013-04-01

Controlling stress responses associated with ischemic changes due to bleeding and ischemia/reperfusion injury is essential for anesthetic management. Endogenous carboxyhemoglobin (COHb) is produced in the oxidative degradation of heme proteins by the stress-response enzyme heme oxygenase. Although the COHb level is elevated in critically ill patients, changes in endogenous COHb during anesthesia have not been well investigated. Therefore, we evaluated changes in endogenous COHb levels in patients undergoing liver resections with inflow occlusion. Levels of COHb were significantly increased after the Pringle maneuver. The inflow occlusion time in patients with increased COHb after the Pringle maneuver (∆COHb > 0.3 %) was significantly longer than in patients without increased COHb (∆COHb < 0.3 %) (P = 0.01). In addition, COHb changes were correlated with inflow occlusion time (P = 0.005, R(2) = 0.21). Neither total blood loss, transfusion volume of packed red blood cells, operation time, nor anesthetic time differed between patients with and without increased COHb. The results indicated that endogenous COHb levels were increased by inflow occlusion in patients undergoing liver resections, which suggests that changes in COHb may correlate with hepatic ischemia/reperfusion injury induced by inflow occlusion.

Crystallographic and optical properties and band diagrams of CuGaS2 and CuGa5S8 phases in Cu-poor Cu2S-Ga2S3 pseudo-binary system

NASA Astrophysics Data System (ADS)

Maeda, Tsuyoshi; Yu, Ying; Chen, Qing; Ueda, Kenta; Wada, Takahiro

2017-04-01

We synthesized Cu-poor Cu-Ga-S samples such, as CuGaS2 and CuGa5S8 with the composition of (1 - x)Cu2S-(x)Ga2S3 with 0.5 ≤ x ≤ 1.0, by a mechanochemical process and sequential heating. The crystal structure changes from tetragonal chalcopyrite-type CuGaS2 (0.5 ≤ x ≤ 0.55) to tetragonal stannite-type CuGa5S8 (x = 0.8). For samples with 0.60 ≤ x ≤ 0.75, the diffraction peaks were identified to be those of a mixed phase of the chalcopyrite- and stannite-type structures. The band-gap energies of Cu-poor Cu-Ga-S samples increase in a stepwise manner with increasing x. The band-gap energy of CuGa5S8 (x = 0.8) with the tetragonal stannite-type structure is approximately 2.66 eV, which is wider than that of chalcopyrite-type CuGaS2 (2.45 eV). The energy levels of valence band maxima (VBMs) were estimated from the ionization energies measured by photoemission yield spectroscopy (PYS). The energy levels of the VBM and conduction band minimum (CBM) of the Cu-poor Cu-Ga-S samples decrease significantly with increasing x (decreasing Cu/Ga ratio). The energy level of the VBM of CuGaS2 (-5.8 eV) is considerably deeper than those of CuInSe2 (-5.2 eV) and CuInS2 (-5.5 eV). The VBM of stannite-type CuGa5S8 with x = 0.8 (-6.4 eV) is much deeper than that of chalcopyrite-type CuGaS2 (-5.8 eV) and stannite-type CuIn3Se5 (-5.6 eV). In order to understand the band structures of chalcopyrite-type CuGaS2 and stannite-type CuGa5S8, we performed first-principles calculations using the Heyd-Scuseria-Ernzerhof (HSE06), nonlocal screened hybrid density functional method. The theoretical band-gap energy of stannite-type CuGa5S8 (2.2 eV) is wider than that of chalcopyrite-type CuGaS2 (2.0 eV). Both the theoretical and experimental band gaps of stannite-type CuGa5S8 are about 0.2 eV wider than those of chalcopyrite-type CuGaS2.

Endogenous TRIM5α Function Is Regulated by SUMOylation and Nuclear Sequestration for Efficient Innate Sensing in Dendritic Cells

PubMed Central

Portilho, Débora M.; Fernandez, Juliette; Ringeard, Mathieu; Machado, Anthony K.; Boulay, Aude; Mayer, Martha; Müller-Trutwin, Michaela; Beignon, Anne-Sophie; Kirchhoff, Frank; Nisole, Sébastien; Arhel, Nathalie J.

2015-01-01

Summary During retroviral infection, viral capsids are subject to restriction by the cellular factor TRIM5α. Here, we show that dendritic cells (DCs) derived from human and non-human primate species lack efficient TRIM5α-mediated retroviral restriction. In DCs, endogenous TRIM5α accumulates in nuclear bodies (NB) that partly co-localize with Cajal bodies in a SUMOylation-dependent manner. Nuclear sequestration of TRIM5α allowed potent induction of type I interferon (IFN) responses during infection, mediated by sensing of reverse transcribed DNA by cGAS. Overexpression of TRIM5α or treatment with the SUMOylation inhibitor ginkgolic acid (GA) resulted in enforced cytoplasmic TRIM5α expression and restored efficient viral restriction but abrogated type I IFN production following infection. Our results suggest that there is an evolutionary trade-off specific to DCs in which restriction is minimized to maximize sensing. TRIM5α regulation via SUMOylation-dependent nuclear sequestration adds to our understanding of how restriction factors are regulated. PMID:26748714

The role of gibberellins in improving the resistance of tebuconazole-coated maize seeds to chilling stress by microencapsulation

NASA Astrophysics Data System (ADS)

Yang, Lijuan; Yang, Daibin; Yan, Xiaojing; Cui, Li; Wang, Zhenying; Yuan, Huizhu

2016-11-01

Chilling stress during germination often causes severe injury. In the present study, maize seed germination and shoot growth under chilling stress were negatively correlated with the dose of tebuconazole in an exponential manner as predicted by the model Y = A + B × e(-x/k). Microencapsulation was an effective means of eliminating potential phytotoxic risk. The gibberellins (GAs) contents were higher after microencapsulation treatment than after conventional treatment when the dose of tebuconazole was higher than 0.12 g AI (active ingredient) kg-1 seed. Further analysis indicated that microencapsulation can stimulate ent-kaurene oxidase (KO) activity to some extent, whereas GA 3-oxidase (GA3ox) and GA 2-oxidase (GA2ox) activities remained similar to those in the control. Genes encoding GA metabolic enzymes exhibited different expression patterns. Transcript levels of ZmKO1 increased in the microcapsule treatments compared to the control. Even when incorporated into microcapsules, tebuconazole led to the upregulation of ZmGA3ox1 at doses of less than 0.12 g AI kg-1 seed and to the upregulation of ZmGA3ox2 when the dose was higher than 0.12 g AI kg-1 seed. With increasing doses of microencapsulated tebuconazole, the transcript levels of ZmGA2ox4, ZmGA2ox5 and ZmGA2ox6 exhibited upward trends, whereas the transcript levels of ZmGA2ox7 exhibited a downward trend.

On the behaviour and origin of the major deep level (EL2) in GaAs

NASA Technical Reports Server (NTRS)

Lagowski, J.; Parsey, J. M.; Kaminska, M.; Wada, K.; Gatos, H. C.

1982-01-01

In an extensive crystal growth and characterization study of Bridgman-grown GaAs it was established that the following factors affect the concentration of the EL2 level: (1) the As pressure during growth; (2) the partial pressure of Ga2O; (3) the concentration of shallow donors and acceptors; and (4) the post-growth cooling cycle. The role of these factors is qualitatively and quantitatively explained by attributing the 0.82 eV donor state to the antisite defect As-sub-Ga formed as a result of Ga-vacancy migration during the post-growth cooling of the crystals.

Depth-resolved ultra-violet spectroscopic photo current-voltage measurements for the analysis of AlGaN/GaN high electron mobility transistor epilayer deposited on Si

NASA Astrophysics Data System (ADS)

Ozden, Burcu; Yang, Chungman; Tong, Fei; Khanal, Min P.; Mirkhani, Vahid; Sk, Mobbassar Hassan; Ahyi, Ayayi Claude; Park, Minseo

2014-10-01

We have demonstrated that the depth-dependent defect distribution of the deep level traps in the AlGaN/GaN high electron mobility transistor (HEMT) epi-structures can be analyzed by using the depth-resolved ultra-violet (UV) spectroscopic photo current-voltage (IV) (DR-UV-SPIV). It is of great importance to analyze deep level defects in the AlGaN/GaN HEMT structure, since it is recognized that deep level defects are the main source for causing current collapse phenomena leading to reduced device reliability. The AlGaN/GaN HEMT epi-layers were grown on a 6 in. Si wafer by metal-organic chemical vapor deposition. The DR-UV-SPIV measurement was performed using a monochromatized UV light illumination from a Xe lamp. The key strength of the DR-UV-SPIV is its ability to provide information on the depth-dependent electrically active defect distribution along the epi-layer growth direction. The DR-UV-SPIV data showed variations in the depth-dependent defect distribution across the wafer. As a result, rapid feedback on the depth-dependent electrical homogeneity of the electrically active defect distribution in the AlGaN/GaN HEMT epi-structure grown on a Si wafer with minimal sample preparation can be elucidated from the DR-UV-SPIV in combination with our previously demonstrated spectroscopic photo-IV measurement with the sub-bandgap excitation.

Gibberellin mediates daylength-controlled differentiation of vegetative meristems in strawberry (Fragaria × ananassa Duch)

PubMed Central

Hytönen, Timo; Elomaa, Paula; Moritz, Thomas; Junttila, Olavi

2009-01-01

Background Differentiation of long and short shoots is an important developmental trait in several species of the Rosaceae family. However, the physiological mechanisms controlling this differentiation are largely unknown. We have studied the role of gibberellin (GA) in regulation of shoot differentiation in strawberry (Fragaria × ananassa Duch.) cv. Korona. In strawberry, differentiation of axillary buds to runners (long shoot) or to crown branches (short shoot) is promoted by long-day and short-day conditions, respectively. Formation of crown branches is a prerequisite for satisfactory flowering because inflorescences are formed from the apical meristems of the crown. Results We found that both prohexadione-calcium and short photoperiod inhibited runner initiation and consequently led to induction of crown branching. In both cases, this correlated with a similar decline in GA1 level. Exogenous GA3 completely reversed the effect of prohexadione-calcium in a long photoperiod, but was only marginally effective in short-day grown plants. However, transfer of GA3-treated plants from short days to long days restored the normal runner formation. This did not occur in plants that were not treated with GA3. We also studied GA signalling homeostasis and found that the expression levels of several GA biosynthetic, signalling and target genes were similarly affected by prohexadione-calcium and short photoperiod in runner tips and axillary buds, respectively. Conclusion GA is needed for runner initiation in strawberry, and the inhibition of GA biosynthesis leads to the formation of crown branches. Our findings of similar changes in GA levels and in GA signalling homeostasis after prohexadione-calcium and short-day treatments, and photoperiod-dependent responsiveness of the axillary buds to GA indicate that GA plays a role also in the photoperiod-regulated differentiation of axillary buds. We propose that tightly regulated GA activity may control induction of cell division in subapical tissues of axillary buds, being one of the signals determining bud fate. PMID:19210764

Ab initio density functional theory study on the atomic and electronic structure of GaP/Si(001) heterointerfaces

NASA Astrophysics Data System (ADS)

Romanyuk, O.; Supplie, O.; Susi, T.; May, M. M.; Hannappel, T.

2016-10-01

The atomic and electronic band structures of GaP/Si(001) heterointerfaces were investigated by ab initio density functional theory calculations. Relative total energies of abrupt interfaces and mixed interfaces with Si substitutional sites within a few GaP layers were derived. It was found that Si diffusion into GaP layers above the first interface layer is energetically unfavorable. An interface with Si/Ga substitution sites in the first layer above the Si substrate is energetically the most stable one in thermodynamic equilibrium. The electronic band structure of the epitaxial GaP/Si(001) heterostructure terminated by the (2 ×2 ) surface reconstruction consists of surface and interface electronic states in the common band gap of two semiconductors. The dispersion of the states is anisotropic and differs for the abrupt Si-Ga, Si-P, and mixed interfaces. Ga 2 p , P 2 p , and Si 2 p core-level binding-energy shifts were computed for the abrupt and the lowest-energy heterointerface structures. Negative and positive core-level shifts due to heterovalent bonds at the interface are predicted for the abrupt Si-Ga and Si-P interfaces, respectively. The distinct features in the heterointerface electronic structure and in the core-level shifts open new perspectives in the experimental characterization of buried polar-on-nonpolar semiconductor heterointerfaces.

Electrical characterisation of deep level defects in Be-doped AlGaAs grown on (100) and (311)A GaAs substrates by MBE

PubMed Central

2011-01-01

The growth of high mobility two-dimensional hole gases (2DHGs) using GaAs-GaAlAs heterostructures has been the subject of many investigations. However, despite many efforts hole mobilities in Be-doped structures grown on (100) GaAs substrate remained considerably lower than those obtained by growing on (311)A oriented surface using silicon as p-type dopant. In this study we will report on the properties of hole traps in a set of p-type Be-doped Al0.29Ga0.71As samples grown by molecular beam epitaxy on (100) and (311)A GaAs substrates using deep level transient spectroscopy (DLTS) technique. In addition, the effect of the level of Be-doping concentration on the hole deep traps is investigated. It was observed that with increasing the Be-doping concentration from 1 × 1016 to 1 × 1017 cm-3 the number of detected electrically active defects decreases for samples grown on (311)A substrate, whereas, it increases for (100) orientated samples. The DLTS measurements also reveal that the activation energies of traps detected in (311)A are lower than those in (100). From these findings it is expected that mobilities of 2DHGs in Be-doped GaAs-GaAlAs devices grown on (311)A should be higher than those on (100). PMID:21711687

First Principles Electronic Structure of Mn doped GaAs, GaP, and GaN Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulthess, Thomas C; Temmerman, Walter M; Szotek, Zdzislawa

We present first-principles electronic structure calculations of Mn doped III-V semiconductors based on the local spin-density approximation (LSDA) as well as the self-interaction corrected local spin density method (SIC-LSD). We find that it is crucial to use a self-interaction free approach to properly describe the electronic ground state. The SIC-LSD calculations predict the proper electronic ground state configuration for Mn in GaAs, GaP, and GaN. Excellent quantitative agreement with experiment is found for magnetic moment and p-d exchange in (GaMn)As. These results allow us to validate commonly used models for magnetic semiconductors. Furthermore, we discuss the delicate problem of extractingmore » binding energies of localized levels from density functional theory calculations. We propose three approaches to take into account final state effects to estimate the binding energies of the Mn-d levels in GaAs. We find good agreement between computed values and estimates from photoemisison experiments.« less

Determination of gallium at trace levels using a spectrofluorimetric method in synthetic U-Ga and Ga-As solutions.

PubMed

Kara, Derya; Fisher, Andrew; Foulkes, Mike; Hill, Steve J

2010-01-01

A simple, easy to use and selective spectrofluorimetric method for the determination of trace levels of gallium has been developed. A new Schiff base, N-o-vanillidine-2-amino-p-cresol (OVAC) was synthesized and its fluorescence activity with gallium investigated. Based on this chelation reaction, a spectrofluorimetric method has been developed for the determination of gallium in synthetically prepared Ga-U and Ga-As samples buffered at pH 4.0 using acetic acid-sodium acetate. The chelation reaction between Ga(III) and N-o-vanillidine-2-amino-p-cresol was very fast, requiring only 30min at room temperature to complex completely. The limit of detection (LOD) (3sigma) for Ga(III) was 7.17 nM (0.50 microgL(-1)), determined from the analysis of 11 different solutions of 20 microg L(-1) Ga(III). Copyright 2009 Elsevier B.V. All rights reserved.

Photocatalysis using a Wide Range of the Visible Light Spectrum: Hydrogen Evolution from Doped AgGaS2.

PubMed

Yamato, Kohei; Iwase, Akihide; Kudo, Akihiko

2015-09-07

Doping of nickel into AgGaS2 yields a new absorption band, at a wavelength longer than the intrinsic absorption band of the AgGaS2 host. The doped nickel forms an electron donor level in a forbidden band of AgGaS2 . The nickel-doped AgGaS2 with rhodium co-catalyst shows photocatalytic activity for sacrificial H2 evolution under the light of up to 760 nm due to the transition from the electron donor level consisting of Ni(2+) to the conduction band of AgGaS2 . Apparent quantum yields for the sacrificial H2 evolution at 540-620 nm are about 1 %. Moreover, the nickel-doped AgGa0.75 In0.25 S2 also responds to near-IR light, up to 900 nm. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theoretical evaluation of two dimensional electron gas characteristics of quaternary AlxInyGa1-x-yN/GaN hetero-junctions

NASA Astrophysics Data System (ADS)

Rahbardar Mojaver, Hassan; Manouchehri, Farzin; Valizadeh, Pouya

2016-04-01

The two dimensional electron gas (2DEG) characteristics of gated metal-face wurtzite AlInGaN/GaN hetero-junctions including positions of subband energy levels, fermi energy level, and the 2DEG concentration as functions of physical and compositional properties of the hetero-junction (i.e., barrier thickness and metal mole-fractions) are theoretically evaluated using the variational method. The calculated values of the 2DEG concentration are in good agreement with the sparsely available experimental data reported in the literature. According to our simulation results, a considerable shift in the positive direction of threshold voltage of AlInGaN/GaN hetero-junction field-effect transistors can be achieved by engineering both the spontaneous and the piezoelectric polarizations using a quaternary AlInGaN barrier-layer of appropriate mole-fractions.

A protective role for nitric oxide and salicylic acid for arsenite phytotoxicity in rice (Oryza sativa L.).

PubMed

Singh, Amit Pal; Dixit, Garima; Kumar, Amit; Mishra, Seema; Kumar, Navin; Dixit, Sameer; Singh, Pradyumna Kumar; Dwivedi, Sanjay; Trivedi, Prabodh Kumar; Pandey, Vivek; Dhankher, Om Prakash; Norton, Gareth J; Chakrabarty, Debasis; Tripathi, Rudra Deo

2017-06-01

Nitric oxide (NO) and salicylic acid (SA) are important signaling molecules in plant system. In the present study both NO and SA showed a protective role against arsenite (As III ) stress in rice plants when supplied exogenously. The application of NO and SA alleviated the negative impact of As III on plant growth. Nitric oxide supplementation to As III treated plants greatly decreased arsenic (As) accumulation in the roots as well as shoots/roots translocation factor. Arsenite exposure in plants decreased the endogenous levels of NO and SA. Exogenous supplementation of SA not only enhanced endogenous level of SA but also the level of NO through enhanced nitrate reductase (NR) activity, whether As III was present or not. Exogenously supplied NO decreased the NR activity and level of endogenous NO. Arsenic accumulation was positively correlated with the expression level of OsLsi1, a transporter responsible for As III uptake. The endogenous level of NO and SA were positively correlated to each other either when As III was present or not. This close relationship indicates that NO and SA work in harmony to modulate the signaling response in As III stressed plants. Copyright © 2017. Published by Elsevier Masson SAS.

Zn-dopant dependent defect evolution in GaN nanowires.

PubMed

Yang, Bing; Liu, Baodan; Wang, Yujia; Zhuang, Hao; Liu, Qingyun; Yuan, Fang; Jiang, Xin

2015-10-21

Zn doped GaN nanowires with different doping levels (0, <1 at%, and 3-5 at%) have been synthesized through a chemical vapor deposition (CVD) process. The effect of Zn doping on the defect evolution, including stacking fault, dislocation, twin boundary and phase boundary, has been systematically investigated by transmission electron microscopy and first-principles calculations. Undoped GaN nanowires show a hexagonal wurtzite (WZ) structure with good crystallinity. Several kinds of twin boundaries, including (101¯3), (101¯1) and (202¯1), as well as Type I stacking faults (…ABABCBCB…), are observed in the nanowires. The increasing Zn doping level (<1 at%) induces the formation of screw dislocations featuring a predominant screw component along the radial direction of the GaN nanowires. At high Zn doping level (3-5 at%), meta-stable cubic zinc blende (ZB) domains are generated in the WZ GaN nanowires. The WZ/ZB phase boundary (…ABABACBA…) can be identified as Type II stacking faults. The density of stacking faults (both Type I and Type II) increases with increasing the Zn doping levels, which in turn leads to a rough-surface morphology in the GaN nanowires. First-principles calculations reveal that Zn doping will reduce the formation energy of both Type I and Type II stacking faults, favoring their nucleation in GaN nanowires. An understanding of the effect of Zn doping on the defect evolution provides an important method to control the microstructure and the electrical properties of p-type GaN nanowires.

Gibberellins Promote Brassinosteroids Action and Both Increase Heterosis for Plant Height in Maize (Zea mays L.)

PubMed Central

Hu, Songlin; Wang, Cuiling; Sanchez, Darlene L.; Lipka, Alexander E.; Liu, Peng; Yin, Yanhai; Blanco, Michael; Lübberstedt, Thomas

2017-01-01

Brassinosteroids (BRs) and Gibberellins (GAs) are two classes of plant hormones affecting plant height (PHT). Thus, manipulation of BR and GA levels or signaling enables optimization of crop grain and biomass yields. We established backcross (BC) families, selected for increased PHT, in two elite maize inbred backgrounds. Various exotic accessions used in the germplasm enhancement in maize project served as donors. BC1-derived doubled haploid lines in the same two elite maize inbred backgrounds established without selection for plant height were included for comparison. We conducted genome-wide association studies to explore the genetic control of PHT by BR and GA. In addition, we used BR and GA inhibitors to compare the relationship between PHT, BR, and GA in inbred lines and heterozygotes from a physiological and biological perspective. A total of 73 genomic loci were discovered to be associated with PHT, with seven co-localized with GA, and two co-localized with BR candidate genes. PHT determined in field trials was significantly correlated with seedling stage BR and GA inhibitor responses. However, this observation was only true for maize heterozygotes, not for inbred lines. Path analysis results suggest that heterozygosity increases GA levels, which in turn promote BR levels. Thus, at least part of heterosis for PHT in maize can be explained by increased GA and BR levels, and seedling stage hormone inhibitor response is promising to predict heterosis for PHT. PMID:28676808

HbA1c and Glycated Albumin Levels Are High in Gastrectomized Subjects with Iron-Deficiency Anemia.

PubMed

Inada, Shinya; Koga, Masafumi

2017-01-01

We report that glycated albumin (GA) is higher relative to HbA1c in non-diabetic, gastrectomized subjects without anemia, and thus is a sign of oxyhyperglycemia. It is known that gastrectomized subjects are prone to iron-deficiency anemia (IDA), and that the HbA1c levels of subjects with IDA are falsely high. In the present study, the HbA1c and GA levels of gastrectomized subjects with IDA were compared with gastrectomized subjects without anemia. Seven non-diabetic gastrectomized subjects with IDA were enrolled in the present study. Twenty-eight non-diabetic gastrectomized subjects without anemia matched with the subjects with IDA in terms of age, gender, and body mass index were used as the controls. Although there were no significant differences in fasting plasma glucose and OGTT 2-hour plasma glucose (2-h PG) between the two groups, the HbA1c and GA levels in gastrectomized subjects with IDA were significantly higher than the controls. For all of the gastrectomized subjects (n=35), ferritin exhibited a significant negative correlation with HbA1c and GA, and a significant positive correlation with 2-h PG. In addition, the HbA1c and GA levels exhibited a significant negative correlation with the mean corpuscular hemoglobin and hemoglobin. The HbA1c and GA levels in gastrectomized subjects with IDA were significantly higher than those in controls. The high GA levels are attributed to a tendency in which patients with total gastrectomy, who are prone to IDA, are susceptible to postprandial hyperglycemia and reactive hypoglycemia, which in turn leads to large fluctuations in plasma glucose. © 2017 by the Association of Clinical Scientists, Inc.

Efficiency droop in GaN LEDs at high injection levels: Role of hydrogen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bochkareva, N. I.; Sheremet, I. A.; Shreter, Yu. G., E-mail: y.shreter@mail.ioffe.ru

2016-10-15

Point defects in GaN and, in particular, their manifestation in the photoluminescence, optical absorption, and recombination current in light-emitting diodes with InGaN/GaN quantum wells are analyzed. The results of this analysis demonstrate that the wide tail of defect states in the band gap of GaN facilitates the trap-assisted tunneling of thermally activated carriers into the quantum well, but simultaneously leads to a decrease in the nonradiative-recombination lifetime and to an efficiency droop as the quasi-Fermi levels intersect the defect states with increasing forward bias. The results reveal the dominant role of hydrogen in the recombination activity of defects with danglingmore » bonds and in the efficiency of GaN-based devices.« less

Establishing a reference range for triiodothyronine levels in preterm infants.

PubMed

Oh, Ki Won; Koo, Mi Sung; Park, Hye Won; Chung, Mi Lim; Kim, Min-ho; Lim, Gina

2014-10-01

Thyroid dysfunction affects clinical complications in preterm infants and older children. However, thyroid hormone replacement in preterm infants has no proven benefits, possibly owing to the lack of an appropriate reference range for thyroid hormone levels. We aimed to establish a reference range for triiodothyronine (T3) levels at 1-month postnatal age (PNA) in preterm infants. This retrospective study included preterm infants born at a tertiary referral neonatal center at gestational age (GA)<35 weeks with no apparent thyroid dysfunction, for 6 consecutive years, with follow-up from PNA 2 weeks to 16 weeks. Using thyroid function tests (TFT), the relationships between T3 levels and thyrotropin (TSH) and free thyroxine (fT4) levels, birth weight, GA, postmenstrual age (PMA), and PNA were examined. The conversion trend for fT4 to T3 was analyzed using the T3/fT4 ratio. Overall, 464 TFTs from 266 infants were analyzed, after excluding 65 infants with thyroid dysfunction. T3 levels increased with fT4 levels, birth weight, GA, PMA, and PNA but not with TSH levels. The T3/fT4 ratio also increased with GA, PNA, and PMA. The average T3 level at 1 month PNA was 72.56 ± 27.83 ng/dL, with significant stratifications by GA. Relatively low T3 and fT4 levels in preterm infants were considered normal, with T3 levels and conversion trends increasing with GA, PMA, and PNA. Further studies are required to confirm the role of the present reference range in thyroid hormone replacement therapy. Copyright © 2014 Elsevier Ltd. All rights reserved.

Ga(+) Basicity and Affinity Scales Based on High-Level Ab Initio Calculations.

PubMed

Brea, Oriana; Mó, Otilia; Yáñez, Manuel

2015-10-26

The structure, relative stability and bonding of complexes formed by the interaction between Ga(+) and a large set of compounds, including hydrocarbons, aromatic systems, and oxygen-, nitrogen-, fluorine and sulfur-containing Lewis bases have been investigated through the use of the high-level composite ab initio Gaussian-4 theory. This allowed us to establish rather accurate Ga(+) cation affinity (GaCA) and Ga(+) cation basicity (GaCB) scales. The bonding analysis of the complexes under scrutiny shows that, even though one of the main ingredients of the Ga(+) -base interaction is electrostatic, it exhibits a non-negligible covalent character triggered by the presence of the low-lying empty 4p orbital of Ga(+) , which favors a charge donation from occupied orbitals of the base to the metal ion. This partial covalent character, also observed in AlCA scales, is behind the dissimilarities observed when GaCA are compared with Li(+) cation affinities, where these covalent contributions are practically nonexistent. Quite unexpectedly, there are some dissimilarities between several Ga(+) -complexes and the corresponding Al(+) -analogues, mainly affecting the relative stability of π-complexes involving aromatic compounds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Landau levels and shallow donor states in GaAs/AlGaAs multiple quantum wells at megagauss magnetic fields

NASA Astrophysics Data System (ADS)

Zybert, M.; Marchewka, M.; Sheregii, E. M.; Rickel, D. G.; Betts, J. B.; Balakirev, F. F.; Gordon, M.; Stier, A. V.; Mielke, C. H.; Pfeffer, P.; Zawadzki, W.

2017-03-01

Landau levels and shallow donor states in multiple GaAs/AlGaAs quantum wells (MQWs) are investigated by means of the cyclotron resonance at megagauss magnetic fields. Measurements of magneto-optical transitions were performed in pulsed fields up to 140 T and temperatures from 6-300 K. The 14 ×14 P.p band model for GaAs is used to interpret free-electron transitions in a magnetic field. Temperature behavior of the observed resonant structure indicates, in addition to the free-electron Landau states, contributions of magnetodonor states in the GaAs wells and possibly in the AlGaAs barriers. The magnetodonor energies are calculated using a variational procedure suitable for high magnetic fields and accounting for conduction band nonparabolicity in GaAs. It is shown that the above states, including their spin splitting, allow one to interpret the observed magneto-optical transitions in MQWs in the middle infrared region. Our experimental and theoretical results at very high magnetic fields are consistent with the picture used previously for GaAs/AlGaAs MQWs at lower magnetic fields.

The localized effect of the Bi level on the valence band in the dilute bismuth GaBixAs1-x alloy

NASA Astrophysics Data System (ADS)

Zhao, Chuan-Zhen; Zhu, Min-Min; Wang, Jun; Wang, Sha-Sha; Lu, Ke-Qing

2018-05-01

The research on the temperature dependence of the band gap energy of the dilute bismuth GaBixAs1-x alloy has been done. It is found that its temperature insensitiveness is due to the enhanced localized character of the valence band state and the small decrease of the temperature coefficient for the conduction band minimum (CBM). The enhanced localized character of the valence band state is the main factor. In order to describe the localized effect of the Bi levels on the valence band, the localized energy is introduced into the Varshni's equation. It is found that the effect of the localized Bi level on the valence band becomes strong with increasing Bi content. In addition, it is found that the pressure dependence of the band gap energy of GaBixAs1-x does not seem to be influenced by the localized Bi levels. It is due to two factors. One is that the pressure dependence of the band gap energy is mainly determined by the D CBM of GaBixAs1-x. The D CBM of GaBixAs1-x is not influenced by the localized Bi levels. The other is that the small variation of the pressure coefficient for the D valence band maximum (VBM) state of GaBixAs1-x can be cancelled by the variation of the pressure coefficient for the D CBM state of GaBixAs1-x.

Gallium 67 citrate scanning and serum angiotensin converting enzyme levels in sarcoidosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, R.G.; Bekerman, C.; Sicilian, L.

1982-09-01

Gallium 67 citrate scans and serum angiotension converting enzyme (ACE) levels were obtained in 54 patients with sarcoidosis and analyzed in relation to clinical manifestation. /sup 67/Ga scans were abnormal in 97% of patients with clinically active disease (n = 30) and in 71% of patients with inactive disease (n = 24). Serum ACE levels were abnormally high (2 standard deviations above the control mean) in 73% of patients with clinically active disease and in 54% of patients with inactive disease. Serum ACE levels correlated significantly with /sup 67/Ga uptake score (r = .436; p < .005). The frequency ofmore » abnormal /sup 67/Ga scans and elevated serum ACE levels suggests that inflammatory activity with little or no clinical expression is common in sarcoidosis. Abnormal /sup 67/Ga scans were highly sensitive (97%) but had poor specificity (29%) to clinical disease activity. The accuracy of negative prediction of clinical activity by normal scans (87%) was better than the accuracy of positive prediction of clinical activity by abnormal scans (63%). /sup 67/Ga scans can be used to support the clinical identification of inactive sarcoidosis.« less

Identification and characterization of a gibberellin-regulated protein, which is ASR5, in the basal region of rice leaf sheaths.

PubMed

Takasaki, Hironori; Mahmood, Tariq; Matsuoka, Makoto; Matsumoto, Hiroshi; Komatsu, Setsuko

2008-04-01

Gibberellins (GAs) regulate growth and development in higher plants. To identify GA-regulated proteins during rice leaf sheath elongation, a proteomic approach was used. Proteins from the basal region of leaf sheath in rice seedling treated with GA(3) were analyzed by fluorescence two-dimensional difference gel electrophoresis. The levels of abscisic acid-stress-ripening-inducible 5 protein (ASR5), elongation factor-1 beta, translationally controlled tumor protein, fructose-bisphosphate aldolase and a novel protein increased; whereas the level of RuBisCO subunit binding-protein decreased by GA(3) treatment. ASR5 out of these six proteins was significantly regulated by GA(3) at the protein level but not at the mRNA level in the basal region of leaf sheaths. Since this protein is regulated not only by abscisic acid but also by GA(3), these results indicate that ASR5 might be involved in plant growth in addition to stress in the basal regions of leaf sheaths.

Relationship between endogenous auxin and cytokinin levels and morphogenic responses inActinidia deliciosa tissue cultures.

PubMed

Centeno, M L; Rodríguez, A; Feito, I; Fernández, B

1996-11-01

Thein vitro culture ofActinidia deliciosa petioles results in a decline of cytokinin content and an increase of auxin levels. The addition of plant growth regulators (PGRs) to the medium lead to recovery of the initial auxin content, and callus induction occurs at the basal end of the explants. Endogenous auxin/cytokinin ratio was higher at this side than in the apical one, due to unequal distribution of endogenous PGRs in the cultured petioles. Some of the induced calluses showed shoot formation when they were transferred to proliferation medium. Most important differences found in hormonal content between organogenic and non-organogenic callus concerned benzyladenine levels. In this paper the relationships between explant behaviour and their hormonal content is discussed.

Deep levels in as-grown and Si-implanted In(0.2)Ga(0.8)As-GaAs strained-layer superlattice optical guiding structures

NASA Technical Reports Server (NTRS)

Dhar, S.; Das, U.; Bhattacharya, P. K.

1986-01-01

Trap levels in about 2-micron In(0.2)Ga(0.8)As(94 A)/GaAs(25 A) strained-layer superlattices, suitable for optical waveguides, have been identified and characterized by deep-level transient spectroscopy and optical deep-level transient spectroscopy measurements. Several dominant electron and hole traps with concentrations of approximately 10 to the 14th/cu cm, and thermal ionization energies Delta-E(T) varying from 0.20 to 0.75 eV have been detected. Except for a 0.20-eV electron trap, which might be present in the In(0.2)Ga(0.8)As well regions, all the other traps have characteristics similar to those identified in molecular-beam epitaxial GaAs. Of these, a 0.42-eV hole trap is believed to originate from Cu impurities, and the others are probably related to native defects. Upon Si implantation and halogen lamp annealing, new deep centers are created. These are electron traps with Delta-E(T) = 0.81 eV and hole traps with Delta-E(T) = 0.46 eV. Traps occurring at room temperature may present limitations for optical devices.

Fermi Level Unpinning of GaSb (100) using Plasma Enhanced Atomic Layer Deposition of Al2O3

DTIC Science & Technology

2010-01-01

of high-/GaSb semiconductor interface. GaSb has a highly reactive surface and on exposure to air it will form a native oxide layer composed of Ga2O3 ...and Sb2O3 2GaSb+3O2→ Ga2O3 +Sb2O3. The Sb2O3 can fur- ther react with the GaSb surface forming elemental Sb and Ga2O3 Sb2O3+2GaSb→ Ga2O3 +4Sb.5,6...rights_and_permissions mentioned before, Sb2O3 reacts with GaSb forming Ga2O3 and elemental Sb.6 The kinetics of this reaction is enhanced at higher temperatures200 °C.14

Potentially life-threatening coagulopathy associated with simultaneous reduction in coagulation and fibrinolytic function in pediatric acute leukemia after hematopoietic stem-cell transplantation.

PubMed

Ishihara, Takashi; Nogami, Keiji; Matsumoto, Tomoko; Nomura, Akitaka; Takeshita, Yasufumi; Ochi, Satoshi; Shima, Midori

2017-07-01

The pathogenesis of sinusoidal obstruction syndrome (SOS) and thrombotic microangiopathy (TMA) after hematopoietic stem cell transplantation (HSCT) is poorly understood, and limited information is available on global hemostatic function in HSCT. We assessed changes in coagulation and fibrinolysis using a simultaneous thrombin and plasmin generation assay (T/P-GA) during HSCT. Measurements of endogenous thrombin potential (T-EP) and plasmin peak height (P-Peak) using T/P-GA in six pediatric acute leukemia patients treated with HSCT were compared to normal plasma. In the SOS case, the ratios of T-EP and P-Peak to normal were simultaneously decreased at four weeks post-HSCT (Pre; ~1.1/1.1-1.4, Week+4; 0.14/0.0084, respectively). Similarly, in the TMA patient, both ratios were decreased at 3 weeks and recovered after 8 weeks (Pre; 1.2/~0.95, Week+3; 0.59/0.22, Week+8; 1.2/0.64-0.85). In the other patients, when SOS/TMA was not evident, the T/P-GA data remained within normal limits. These findings suggest that the simultaneous reduction of coagulation and fibrinolytic function in patients developing SOS/TMA can lead to a life-threatening coagulopathy. Further research is warranted to clarify global hemostatic function after HSCT to establish optimal supportive therapy for these critical clinical disorders of hemostasis.

Resilience of Penicillium resedanum LK6 and exogenous gibberellin in improving Capsicum annuum growth under abiotic stresses.

PubMed

Khan, Abdul Latif; Waqas, Muhammad; Lee, In-Jung

2015-03-01

Understanding how endophytic fungi mitigate abiotic stresses in plants will be important in a changing global climate. A few endophytes can produce phytohormones, but their ability to induce physiological changes in host plants during extreme environmental conditions are largely unexplored. In the present study, we investigated the ability of Penicillium resedanum LK6 to produce gibberellins and its role in improving the growth of Capsicum annuum L. under salinity, drought, and heat stresses. These effects were compared with exogenous application of gibberellic acid (GA3). Endophyte treatment significantly increased shoot length, biomass, chlorophyll content, and the photosynthesis rate compared with the uninfected control during abiotic stresses. The endophyte and combined endophyte + GA3 treatments significantly ameliorated the negative effects of stresses compared with the control. Stress-responsive endogenous abscisic acid and its encoding genes, such as zeaxanthin epoxidase, 9-cis-epoxycarotenoid dioxygenase 3, and ABA aldehyde oxidase 3, were significantly reduced in endophyte-treated plants under stress. Conversely, salicylic acid and biosynthesis-related gene (isochorismate synthase) had constitutive expressions while pathogenesis related (PR1 and PR5) genes showed attenuated responses during endophyte treatment under abiotic stresses. The present findings suggest that endophytes have effects comparable to those of exogenous GA3; both can significantly increase plant growth and yield under changing environmental conditions by reprogramming the host plant's physiological responses.

Capacitance spectroscopy on n-type GaNAs/GaAs embedded quantum structure solar cells

NASA Astrophysics Data System (ADS)

Venter, Danielle; Bollmann, Joachim; Elborg, Martin; Botha, J. R.; Venter, André

2018-04-01

In this study, both deep level transient spectroscopy (DLTS) and admittance spectroscopy (AS) have been used to study the properties of electrically active deep level centers present in GaNAs/GaAs quantum wells (QWs) embedded in p-i-n solar cells. The structures were grown by molecular beam epitaxy (MBE). In particular, the electrical properties of samples with Si (n-type) doping of the QWs were investigated. DLTS revealed four deep level centers in the material, whereas only three were detected by AS. NextNano++ simulation software was used to model the sample band-diagrams to provide reasoning for the origin of the signals produced by both techniques.

Energy states, transport, and magnetotransport in diluted magnetic semiconductor (Ga, Mn)As with quantum well InGaAs.

PubMed

Shchurova, L Yu; Kulbachinskii, V A

2011-03-01

We investigate energy levels, thermodynamic, transport and magnetotransport properties of holes in GaAs structure with quantum well InGaAs delta-doped by C and Mn. We present self-consistent calculations for energy levels in the quantum well for different degrees of ionization of Mn impurity. The magnetoresistance of holes in the quantum well is calculated. We explain observed negative magnetoresistance by the reduction of spin-flip scattering on magnetic ions due to aligning of spins with magnetic field.

Mechanism of internal browning of pineapple: The role of gibberellins catabolism gene (AcGA2ox) and GAs

PubMed Central

Zhang, Qin; Rao, Xiuwen; Zhang, Lubin; He, Congcong; Yang, Fang; Zhu, Shijiang

2016-01-01

Internal browning (IB), a physiological disorder (PD) that causes severe losses in harvested pineapple, can be induced by exogenous gibberellins (GAs). Over the years, studies have focused on roles of Gibberellin 2-oxidase (GA2oxs), the major GAs catabolic enzyme in plants, in the regulation of changes in morphology or biomass. However, whether GA2oxs could regulate PD has not been reported. Here, a full-length AcGA2ox cDNA was isolated from pineapple, with the putative protein sharing 23.59% to 72.92% identity with GA2oxs from five other plants. Pineapples stored at 5 °C stayed intact, while those stored at 20 °C showed severe IB. Storage at 5 °C enhanced AcGA2ox expression and decreased levels of a GAs (GA4) ‘compared with storage at 20 °C. However, at 20 °C, exogenous application of abscisic acid (ABA) significantly suppressed IB. ABA simultaneously upregulated AcGA2ox and reduced GA4. Ectopic expression of AcGA2ox in Arabidopsis resulted in reduced GA4, lower seed germination, and shorter hypocotyls and roots, all of which were restored by exogenous GA4/7. Moreover, in pineapple, GA4/7 upregulated polyphenol oxidase, while storage at 5 °C and ABA downregulated it. These results strongly suggest the involvement of AcGA2ox in regulation of GAs levels and a role of AcGA2ox in regulating IB. PMID:27982026

Glutathione and abscisic acid supplementation influences somatic embryo maturation and hormone endogenous levels during somatic embryogenesis in Podocarpus lambertii Klotzsch ex Endl.

PubMed

Fraga, Hugo Pacheco de Freitas; Vieira, Leila do Nascimento; Puttkammer, Catarina Corrêa; Dos Santos, Henrique Pessoa; Garighan, Julio de Andrade; Guerra, Miguel Pedro

2016-12-01

Here we propose a protocol for embryogenic cultures induction, proliferation and maturation for the Brazilian conifer Podocarpus lambertii, and investigated the effect of abscisic acid (ABA) and glutathione (GSH) supplementation on the maturation phase. ABA, zeatin (Z) and salicylic acid (SA) endogenous levels were quantified. Number of somatic embryos obtained in ABA-supplemented treatment was significant higher than in ABA-free treatment, showing the relevance of ABA supplementation during somatic embryos maturation. Histological analysis showed the stereotyped sequence of developmental stages in conifer somatic embryos, reaching the late torpedo-staged embryo. GSH supplementation in maturation culture medium improved the somatic embryos number and morphological features. GSH 0mM and GSH 0.1mM treatments correlated with a decreased ABA endogenous level during maturation, while GSH 0.5mM treatment showed constant levels. All treatments resulted in decreased Z endogenous levels, supporting the concept that cytokinins are important during the initial cell division but not for the later stages of embryo development. The lowest SA levels found in GSH 0.5mM treatment were coincident with early embryonic development, and this treatment resulted in the highest development of somatic embryos. Thus, a correlation between lower SA levels and improved somatic embryo formation can be hypothesized. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

A model of the endogenous glucose balance incorporating the characteristics of glucose transporters.

PubMed

Arleth, T; Andreassen, S; Federici, M O; Benedetti, M M

2000-07-01

This paper describes the development and preliminary test of a model of the endogenous glucose balance that incorporates the characteristics of the glucose transporters GLUT1, GLUT3 and GLUT4. In the modeling process the model is parameterized with nine parameters that are subsequently estimated from data in the literature on the hepatic- and endogenous- balances at various combinations of blood glucose and insulin levels. The ability of the resulting endogenous balance to fit blood glucose measured from patients was tested on 20 patients. The fit obtained with this model compared favorably with the fit obtained with the endogenous balance currently incorporated in the DIAS system.

Salt Stress Represses Soybean Seed Germination by Negatively Regulating GA Biosynthesis While Positively Mediating ABA Biosynthesis

PubMed Central

Shu, Kai; Qi, Ying; Chen, Feng; Meng, Yongjie; Luo, Xiaofeng; Shuai, Haiwei; Zhou, Wenguan; Ding, Jun; Du, Junbo; Liu, Jiang; Yang, Feng; Wang, Qiang; Liu, Weiguo; Yong, Taiwen; Wang, Xiaochun; Feng, Yuqi; Yang, Wenyu

2017-01-01

Soybean is an important and staple oilseed crop worldwide. Salinity stress has adverse effects on soybean development periods, especially on seed germination and post-germinative growth. Improving seed germination and emergence will have positive effects under salt stress conditions on agricultural production. Here we report that NaCl delays soybean seed germination by negatively regulating gibberellin (GA) while positively mediating abscisic acid (ABA) biogenesis, which leads to a decrease in the GA/ABA ratio. This study suggests that fluridone (FLUN), an ABA biogenesis inhibitor, might be a potential plant growth regulator that can promote soybean seed germination under saline stress. Different soybean cultivars, which possessed distinct genetic backgrounds, showed a similar repressed phenotype during seed germination under exogenous NaCl application. Biochemical analysis revealed that NaCl treatment led to high MDA (malondialdehyde) level during germination and the post-germinative growth stages. Furthermore, catalase, superoxide dismutase, and peroxidase activities also changed after NaCl treatment. Subsequent quantitative Real-Time Polymerase Chain Reaction analysis showed that the transcription levels of ABA and GA biogenesis and signaling genes were altered after NaCl treatment. In line with this, phytohormone measurement also revealed that NaCl considerably down-regulated active GA1, GA3, and GA4 levels, whereas the ABA content was up-regulated; and therefore ratios, such as GA1/ABA, GA3/ABA, and GA4/ABA, are decreased. Consistent with the hormonal quantification, FLUN partially rescued the delayed-germination phenotype caused by NaCl-treatment. Altogether, these results demonstrate that NaCl stress inhibits soybean seed germination by decreasing the GA/ABA ratio, and that FLUN might be a potential plant growth regulator that could promote soybean seed germination under salinity stress. PMID:28848576

Salt Stress Represses Soybean Seed Germination by Negatively Regulating GA Biosynthesis While Positively Mediating ABA Biosynthesis.

PubMed

Shu, Kai; Qi, Ying; Chen, Feng; Meng, Yongjie; Luo, Xiaofeng; Shuai, Haiwei; Zhou, Wenguan; Ding, Jun; Du, Junbo; Liu, Jiang; Yang, Feng; Wang, Qiang; Liu, Weiguo; Yong, Taiwen; Wang, Xiaochun; Feng, Yuqi; Yang, Wenyu

2017-01-01

Soybean is an important and staple oilseed crop worldwide. Salinity stress has adverse effects on soybean development periods, especially on seed germination and post-germinative growth. Improving seed germination and emergence will have positive effects under salt stress conditions on agricultural production. Here we report that NaCl delays soybean seed germination by negatively regulating gibberellin (GA) while positively mediating abscisic acid (ABA) biogenesis, which leads to a decrease in the GA/ABA ratio. This study suggests that fluridone (FLUN), an ABA biogenesis inhibitor, might be a potential plant growth regulator that can promote soybean seed germination under saline stress. Different soybean cultivars, which possessed distinct genetic backgrounds, showed a similar repressed phenotype during seed germination under exogenous NaCl application. Biochemical analysis revealed that NaCl treatment led to high MDA (malondialdehyde) level during germination and the post-germinative growth stages. Furthermore, catalase, superoxide dismutase, and peroxidase activities also changed after NaCl treatment. Subsequent quantitative Real-Time Polymerase Chain Reaction analysis showed that the transcription levels of ABA and GA biogenesis and signaling genes were altered after NaCl treatment. In line with this, phytohormone measurement also revealed that NaCl considerably down-regulated active GA 1 , GA 3 , and GA 4 levels, whereas the ABA content was up-regulated; and therefore ratios, such as GA 1 /ABA, GA 3 /ABA, and GA 4 /ABA, are decreased. Consistent with the hormonal quantification, FLUN partially rescued the delayed-germination phenotype caused by NaCl-treatment. Altogether, these results demonstrate that NaCl stress inhibits soybean seed germination by decreasing the GA/ABA ratio, and that FLUN might be a potential plant growth regulator that could promote soybean seed germination under salinity stress.

Open-Gated pH Sensor Fabricated on an Undoped-AlGaN/GaN HEMT Structure

PubMed Central

Abidin, Mastura Shafinaz Zainal; Hashim, Abdul Manaf; Sharifabad, Maneea Eizadi; Rahman, Shaharin Fadzli Abd; Sadoh, Taizoh

2011-01-01

The sensing responses in aqueous solution of an open-gated pH sensor fabricated on an AlGaN/GaN high-electron-mobility-transistor (HEMT) structure are investigated. Under air-exposed ambient conditions, the open-gated undoped AlGaN/GaN HEMT only shows the presence of a linear current region. This seems to show that very low Fermi level pinning by surface states exists in the undoped AlGaN/GaN sample. In aqueous solution, typical current-voltage (I-V) characteristics with reasonably good gate controllability are observed, showing that the potential of the AlGaN surface at the open-gated area is effectively controlled via aqueous solution by the Ag/AgCl gate electrode. The open-gated undoped AlGaN/GaN HEMT structure is capable of distinguishing pH level in aqueous electrolytes and exhibits linear sensitivity, where high sensitivity of 1.9 mA/pH or 3.88 mA/mm/pH at drain-source voltage, VDS = 5 V is obtained. Due to the large leakage current where it increases with the negative gate voltage, Nernstian like sensitivity cannot be determined as commonly reported in the literature. This large leakage current may be caused by the technical factors rather than any characteristics of the devices. Surprisingly, although there are some imperfections in the device preparation and measurement, the fabricated devices work very well in distinguishing the pH levels. Suppression of current leakage by improving the device preparation is likely needed to improve the device performance. The fabricated device is expected to be suitable for pH sensing applications. PMID:22163786

PSA levels as a predictor of 68Ga PSMA PET/CT positivity in patients with prostate cancer?

PubMed

Soydal, Cigdem; Urun, Yuksel; Suer, Evren; Nak, Demet; Ozkan, Elgin; Kucuk, Ozlem N

2018-05-10

The aim of this study is to evaluate predictive factors of 68Gallium (68Ga) Prostate-Specific Membrane Antigen (PSMA) Positron Emission Tomography (PET)/Computed Tomography (CT) positivity. Relationships between serum Prostate Specific Antigen (PSA), Lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) levels, Gleason Score (GS) and positivity of 68Ga PSMA PET in patients who underwent 68Ga PSMA PET/CT for restaging for PCa were evaluated retrospectively. One hundred and four (median age: 67; range: 51-88) patients were included in this study. Of these patients, PSMA PET was positive in 75 (72%) patients. Mean serum PSA levels for PET negative and positive groups were 0.76±1.00 and 180.85±324.93 ng/ml (p<0.001). The sensitivity and specificity of 68Ga PSMA PET/CT for detection of disease recurrence were calculated as 92% and 80%, respectively, for the 1.4 ng/ml PSA cut-off and 92% and 90%, respectively, for the 2 ng/ml PSA cut-off values. The positivity rates for patients with PSA levels <1.4 ng/ml and ≥1.4 ng/ml were 21% and 90%, respectively (p<0.001). 68Ga PSMA PET/CT seems to be a highly sensitive in patients with early PSA recurrence. Patients with higher GS and early PSA recurrence could benefit from 68Ga PSMA PET/CT.

Wavelength-modulated photocapacitance spectroscopy

NASA Technical Reports Server (NTRS)

Kamieniecki, E.; Lagowski, J.; Gatos, H. C.

1980-01-01

Derivative deep-level spectroscopy was achieved with wavelength-modulated photocapacitance employing MOS structures and Schottky barriers. The energy position and photoionization characteristics of deep levels of melt-grown GaAs and the Cr level in high-resistivity GaAs were determined. The advantages of this method over existing methods for deep-level spectroscopy are discussed.

Theoretical and experimental studies of electric field distribution in N-polar GaN/AlGaN/GaN heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gladysiewicz, M., E-mail: marta.gladysiewicz@pwr.edu.pl; Janicki, L.; Kudrawiec, R.

2015-12-28

Electric field distribution in N-polar GaN(channel)/AlGaN/GaN(buffer) heterostructures was studied theoretically by solving Schrodinger and Poisson equations in a self-consistent manner for various boundary conditions and comparing results of these calculations with experimental data, i.e., measurements of electric field in GaN(channel) and AlGaN layers by electromodulation spectroscopy. A very good agreement between theoretical calculations and experimental data has been found for the Fermi-level located at ∼0.3 eV below the conduction band at N-polar GaN surface. With this surface boundary condition, the electric field distribution and two dimensional electron gas concentration are determined for GaN(channel)/AlGaN/GaN(buffer) heterostructures of various thicknesses of GaN(channel) and AlGaNmore » layers.« less

Glycyrrhetinic acid prevents cutaneous scratching behavior in mice elicited by substance P or PAR-2 agonist.

PubMed

Akasaka, Yuko; Yoshida, Tsuyoshi; Tsukahara, Michiko; Hatta, Akira; Inoue, Hideo

2011-11-16

Although glycyrrhetinic acid (GA) has been used for the prevention of itch in chronic dermatitis, the mechanism underlying the antipruritic effects of GA is still unclear. Recently, several mediators other than histamine, such as substance P and tryptase, were found to participate in chronic itch. Here, we investigated the effect of GA on pruritus induced by various pruritic agents including histamine in mice. We also determined the level of leukotriene (LT)B(4) in mouse skin injected with substance P in an effort to uncover part of the antipruritic mechanism of GA. Scratching events were counted for 10 min after intradermal injection of histamine, substance P (100 nmol per site each), protease-activated receptor-2 (PAR-2) agonistic peptide (50 nmol per site), or LTB(4) (0.03 nmol per site) with or without GA (4 nmol per site) into male ICR mice. Levels of LTB(4) in the skin after injection of substance P were determined by ELISA. GA did not suppress scratching behavior induced by histamine and LTB(4), but markedly and dose-dependently suppressed that induced by substance P and PAR-2 agonistic peptide. LTB(4) levels in skin elevated by substance P were lowered by GA. These data support the efficacy of GA in counteracting itch in chronic dermatitis because GA reduced scratching behavior induced by substance P and PAR-2 agonistic peptide. GA may exert antipruritic effects via inhibition of LTB(4) production in skin. Copyright © 2011 Elsevier B.V. All rights reserved.

Effect of feeding level on ileal and total tract digestibility of nutrients and energy from soybean meal-based diets for piglets.

PubMed

Goerke, M; Mosenthin, R; Jezierny, D; Sauer, N; Piepho, H-P; Messerschmidt, U; Eklund, M

2014-12-01

A total of 36 piglets with an initial body weight (BW) of 5.6 ± 0.7 kg, fitted with simple T-cannulas at the distal ileum, were used to evaluate the effect of three graded feeding levels (50, 75 or 100 g/kg BW(0.75) day) on apparent ileal digestibility (AID) and total tract digestibility (ATTD) of dry matter (DM), nitrogen (N) and energy, and on ATTD of organic matter (OM), ether extracts (EE), neutral detergent fibre (NDF), acid detergent fibre (ADF) and digestible (DE), metabolisable (ME) and net energy (NE) content in soybean meal (SBM)-casein-cornstarch-based diets. The AID of DM, N and energy and ATTD of NDF, ADF and EE in the diets were not affected (p > 0.05) by the feed intake (FI) level. There was a small decrease in ATTD of DM, N (CP), OM, ash and energy, and in DE, ME and NE content in the diets (p < 0.05) with increasing FI level. The net disappearance in the large intestine (in % of ileal recovery) decreased for DM, N and energy (p < 0.05) with increasing FI level. The design of the study allowed for estimating ileal endogenous loss of N and total tract endogenous loss of ash, N and EE, for estimating corresponding true ileal and total tract digestibility values, and for estimating urinary endogenous N loss. High variability in estimates of ileal endogenous N loss and total tract endogenous losses of N, EE and ash reflects great variation in individual endogenous losses between animals. Estimation of true total tract digestibility of N, EE and ash by regression analysis was affected by their decrease in ATTD with increasing FI level, as estimates for true digestibility were lower compared to their apparent values. The present results suggest that FI level can affect both apparent and true total tract nutrient digestibility in piglets. Journal of Animal Physiology and Animal Nutrition © 2014 Blackwell Verlag GmbH.

Multi-shell spherical GaAs /AlxGa1-x As quantum dot shells-size distribution as a mechanism to generate intermediate band energy levels

NASA Astrophysics Data System (ADS)

Rodríguez-Magdaleno, K. A.; Pérez-Álvarez, R.; Martínez-Orozco, J. C.; Pernas-Salomón, R.

2017-04-01

In this work the generation of an intermediate band of energy levels from multi-shell spherical GaAs /AlxGa1-x As quantum dot shells-size distribution is reported. Within the effective mass approximation the electronic structure of a GaAs spherical quantum-dot surrounded by one, two and three shells is studied in detail using a numerically stable transfer matrix method. We found that a shells-size distribution characterized by continuously wider GaAs domains is a suitable mechanism to generate the intermediate band whose width is also dependent on the Aluminium concentration x. Our results suggest that this effective mechanism can be used for the design of wider intermediate band than reported in other quantum systems with possible solar cells enhanced performance.

Atomic-scale structural and electronic properties of SrTiO3/GaAs interfaces: A combined STEM-EELS and first-principles study

NASA Astrophysics Data System (ADS)

Hong, Liang; Bhatnagar, Kunal; Droopad, Ravi; Klie, Robert F.; Öǧüt, Serdar

2017-07-01

The electronic properties of epitaxial oxide thin films grown on compound semiconductors are largely determined by the interfacial atomic structure, as well as the thermodynamic conditions during synthesis. Ferroelectric polarization and Fermi-level pinning in SrTiO3 films have been attributed to the presence of oxygen vacancies at the oxide/semiconductor interface. Here, we present scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy analyses of GaAs films grown on SrTiO3 combined with first-principles calculations to determine the atomic and electronic structures of the SrTiO3/GaAs interfaces. An atomically abrupt SrO/As interface is observed and the interfacial SrO layer is found to be O-deficient. First-principles density functional theory (DFT) calculations show SrO/Ga and Sr/As interfaces are favorable under O-rich and O-poor conditions, respectively. The SrO/Ga interface is reconstructed via the formation of Ga-Ga dimers while the Sr/As interface is abrupt and consistent with the experiment. DFT calculations further reveal that intrinsic two-dimensional electron gas (2DEG) forms in both SrO/Ga and Sr/As interfaces, and the Fermi level is pinned to the localized 2DEG states. Interfacial O vacancies can enhance the 2DEG density while it is possible for Ga/As vacancies to unpin the Fermi level from the 2DEG states.

The trap states in lightly Mg-doped GaN grown by MOVPE on a freestanding GaN substrate

NASA Astrophysics Data System (ADS)

Narita, Tetsuo; Tokuda, Yutaka; Kogiso, Tatsuya; Tomita, Kazuyoshi; Kachi, Tetsu

2018-04-01

We investigated traps in lightly Mg-doped (2 × 1017 cm-3) p-GaN fabricated by metalorganic vapor phase epitaxy (MOVPE) on a freestanding GaN substrate and the subsequent post-growth annealing, using deep level transient spectroscopy. We identified four hole traps with energy levels of EV + 0.46, 0.88, 1.0, and 1.3 eV and one electron trap at EC - 0.57 eV in a p-type GaN layer uniformly doped with magnesium (Mg). The Arrhenius plot of hole traps with the highest concentration (˜3 × 1016 cm-3) located at EV + 0.88 eV corresponded to those of hole traps ascribed to carbon on nitrogen sites in n-type GaN samples grown by MOVPE. In fact, the range of the hole trap concentrations at EV + 0.88 eV was close to the carbon concentration detected by secondary ion mass spectroscopy. Moreover, the electron trap at EC - 0.57 eV was also identical to the dominant electron traps commonly observed in n-type GaN. Together, these results suggest that the trap states in the lightly Mg-doped GaN grown by MOVPE show a strong similarity to those in n-type GaN, which can be explained by the Fermi level close to the conduction band minimum in pristine MOVPE grown samples due to existing residual donors and Mg-hydrogen complexes.

The site of net absorption of Ca from the intestinal tract of growing pigs and effect of phytic acid, Ca level and Ca source on Ca digestibility.

PubMed

González-Vega, J Caroline; Walk, Carrie L; Liu, Yanhong; Stein, Hans H

2014-01-01

An experiment was conducted to test the hypothesis that the standardised digestibility of Ca in calcium carbonate and Lithothamnium calcareum Ca is not different regardless of the level of dietary Ca, and that phytic acid affects the digestibility of Ca in these two ingredients to the same degree. The objectives were to determine where in the intestinal tract Ca absorption takes place and if there are measurable quantities of basal endogenous Ca fluxes in the stomach, small intestine or large intestine. Diets contained calcium carbonate or L. calcareum Ca as the sole source of Ca, 0% or 1% phytic acid and 0.4% or 0.8% Ca. A Ca-free diet was also formulated and used to measure endogenous fluxes and losses of Ca. Nine growing pigs (initial body weight 23.8 ± 1.3 kg) were cannulated in the duodenum and in the distal ileum, and faecal, ileal and duodenal samples were collected. Duodenal endogenous fluxes of Ca were greater (p < 0.05) than ileal endogenous fluxes and total tract endogenous losses of Ca, but ileal endogenous fluxes were less (p < 0.05) than total tract endogenous losses. Standardised digestibility of Ca was not affected by the level of phytic acid, but decreased (p < 0.05) as Ca level increased in L. calcareum Ca diets, but that was not the case if calcium carbonate was the source of Ca (interaction, p < 0.05). The standardised duodenal digestibility (SDD), standardised ileal digestibility (SID) and standardised total tract digestibility (STTD) of Ca were not different if calcium carbonate was the source of dietary Ca. However, the STTD of Ca in L. calcareum Ca was greater (p < 0.05) than the SID and SDD of Ca. The SDD, SID and STTD of Ca in calcium carbonate were greater (p < 0.05) than those of L. calcareum Ca. In conclusion, under the conditions of this experiment, standardised digestibility of Ca is not affected by the level of phytic acid, but may be affected by dietary Ca level depending on the Ca source. Calcium from calcium carbonate is mostly absorbed before the duodenum, but Ca from L. calcareum Ca is mostly absorbed in the jejunum and ileum.

Differential RISC association of endogenous human microRNAs predicts their inhibitory potential

PubMed Central

Flores, Omar; Kennedy, Edward M.; Skalsky, Rebecca L.; Cullen, Bryan R.

2014-01-01

It has previously been assumed that the generally high stability of microRNAs (miRNAs) reflects their tight association with Argonaute (Ago) proteins, essential components of the RNA-induced silencing complex (RISC). However, recent data have suggested that the majority of mature miRNAs are not, in fact, Ago associated. Here, we demonstrate that endogenous human miRNAs vary widely, by >100-fold, in their level of RISC association and show that the level of Ago binding is a better indicator of inhibitory potential than is the total level of miRNA expression. While miRNAs of closely similar sequence showed comparable levels of RISC association in the same cell line, these varied between different cell types. Moreover, the level of RISC association could be modulated by overexpression of complementary target mRNAs. Together, these data indicate that the level of RISC association of a given endogenous miRNA is regulated by the available RNA targetome and predicts miRNA function. PMID:24464996

Differential RISC association of endogenous human microRNAs predicts their inhibitory potential.

PubMed

Flores, Omar; Kennedy, Edward M; Skalsky, Rebecca L; Cullen, Bryan R

2014-04-01

It has previously been assumed that the generally high stability of microRNAs (miRNAs) reflects their tight association with Argonaute (Ago) proteins, essential components of the RNA-induced silencing complex (RISC). However, recent data have suggested that the majority of mature miRNAs are not, in fact, Ago associated. Here, we demonstrate that endogenous human miRNAs vary widely, by >100-fold, in their level of RISC association and show that the level of Ago binding is a better indicator of inhibitory potential than is the total level of miRNA expression. While miRNAs of closely similar sequence showed comparable levels of RISC association in the same cell line, these varied between different cell types. Moreover, the level of RISC association could be modulated by overexpression of complementary target mRNAs. Together, these data indicate that the level of RISC association of a given endogenous miRNA is regulated by the available RNA targetome and predicts miRNA function.

Transgenesis affects endogenous soybean allergen levels less than traditional breeding.

PubMed

Hill, Ryan C; Fast, Brandon J; Herman, Rod A

2017-10-01

The regulatory body that oversees the safety assessment of genetically modified (GM) crops in the European Union, the European Food Safety Authority (EFSA), uniquely requires that endogenous allergen levels be quantified as part of the compositional characterization of GM versions of crops, such as soybean, that are considered to be major allergenic foods. The value of this requirement for assessing food safety has been challenged for multiple reasons including negligible risk of altering allergen levels compared with traditional non-GM breeding. Scatter plots comparing the mean endogenous allergen levels in non-GM soybean isoline grain with the respective levels in GM grain or concurrently grown non-GM commercial reference varieties clearly show that transgenesis causes less change compared with traditional breeding. This visual assessment is confirmed by the quantitative fit of the line of identity (y = x) to the datasets. The current science on allergy does not support the requirement for quantifying allergen levels in GM crops to support safety assessment. Copyright © 2017 Elsevier Inc. All rights reserved.

p -n Junction Rectifying Characteristics of Purely n -Type GaN-Based Structures

NASA Astrophysics Data System (ADS)

Zuo, P.; Jiang, Y.; Ma, Z. G.; Wang, L.; Zhao, B.; Li, Y. F.; Yue, G.; Wu, H. Y.; Yan, H. J.; Jia, H. Q.; Wang, W. X.; Zhou, J. M.; Sun, Q.; Liu, W. M.; Ji, An-Chun; Chen, H.

2017-08-01

The GaN-based p -n junction rectifications are important in the development of high-power electronics. Here, we demonstrate that p -n junction rectifying characteristics can be realized with pure n -type structures by inserting an (In,Ga)N quantum well into the GaN /(Al ,Ga )N /GaN double heterostructures. Unlike the usual barriers, the insertion of an (In,Ga)N quantum well, which has an opposite polarization field to that of the (Al,Ga)N barrier, tailors significantly the energy bands of the system. The lifted energy level of the GaN spacer and the formation of the (In ,Ga )N /GaN interface barrier can improve the reverse threshold voltage and reduce the forward threshold voltage simultaneously, forming the p -n junction rectifying characteristics.

High temperature and low pressure chemical vapor deposition of silicon nitride on AlGaN: Band offsets and passivation studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, Pramod; Washiyama, Shun; Kaess, Felix

2016-04-14

In this work, we employed X-ray photoelectron spectroscopy to determine the band offsets and interface Fermi level at the heterojunction formed by stoichiometric silicon nitride deposited on Al{sub x}Ga{sub 1-x}N (of varying Al composition “x”) via low pressure chemical vapor deposition. Silicon nitride is found to form a type II staggered band alignment with AlGaN for all Al compositions (0 ≤ x ≤ 1) and present an electron barrier into AlGaN even at higher Al compositions, where E{sub g}(AlGaN) > E{sub g}(Si{sub 3}N{sub 4}). Further, no band bending is observed in AlGaN for x ≤ 0.6 and a reduced band bending (by ∼1 eV in comparison to that atmore » free surface) is observed for x > 0.6. The Fermi level in silicon nitride is found to be at 3 eV with respect to its valence band, which is likely due to silicon (≡Si{sup 0/−1}) dangling bonds. The presence of band bending for x > 0.6 is seen as a likely consequence of Fermi level alignment at Si{sub 3}N{sub 4}/AlGaN hetero-interface and not due to interface states. Photoelectron spectroscopy results are corroborated by current-voltage-temperature and capacitance-voltage measurements. A shift in the interface Fermi level (before band bending at equilibrium) from the conduction band in Si{sub 3}N{sub 4}/n-GaN to the valence band in Si{sub 3}N{sub 4}/p-GaN is observed, which strongly indicates a reduction in mid-gap interface states. Hence, stoichiometric silicon nitride is found to be a feasible passivation and dielectric insulation material for AlGaN at any composition.« less

Circulating Hepcidin-25 Is Reduced by Endogenous Estrogen in Humans.

PubMed

Lehtihet, Mikael; Bonde, Ylva; Beckman, Lena; Berinder, Katarina; Hoybye, Charlotte; Rudling, Mats; Sloan, John H; Konrad, Robert J; Angelin, Bo

2016-01-01

Hepcidin reduces iron absorption by binding to the intestinal iron transporter ferroportin, thereby causing its degradation. Although short-term administration of testosterone or growth hormone (GH) has been reported to decrease circulating hepcidin levels, little is known about how hepcidin is influenced in human endocrine conditions associated with anemia. We used a sensitive and specific dual-monoclonal antibody sandwich immunoassay to measure hepcidin-25 in patients (a) during initiation of in vitro fertilization when endogenous estrogens were elevated vs. suppressed, (b) with GH deficiency before and after 12 months substitution treatment, (c) with hyperthyroidism before and after normalization, and (d) with hyperprolactinemia before and after six months of treatment with a dopamine agonist. In response to a marked stimulation of endogenous estrogen production, median hepcidin levels decreased from 4.85 to 1.43 ng/mL (p < 0.01). Hyperthyroidism, hyperprolactinemia, or GH substitution to GH-deficient patients did not influence serum hepcidin-25 levels. In humans, gonadotropin-stimulated endogenous estrogen markedly decreases circulating hepcidin-25 levels. No clear and stable correlation between iron biomarkers and hepcidin-25 was seen before or after treatment of hyperthyroidism, hyperprolactinemia or growth hormone deficiency.

Circulating Hepcidin-25 Is Reduced by Endogenous Estrogen in Humans

PubMed Central

Lehtihet, Mikael; Bonde, Ylva; Beckman, Lena; Berinder, Katarina; Hoybye, Charlotte; Rudling, Mats; Sloan, John H.; Konrad, Robert J.; Angelin, Bo

2016-01-01

Objective Hepcidin reduces iron absorption by binding to the intestinal iron transporter ferroportin, thereby causing its degradation. Although short-term administration of testosterone or growth hormone (GH) has been reported to decrease circulating hepcidin levels, little is known about how hepcidin is influenced in human endocrine conditions associated with anemia. Research design and methods We used a sensitive and specific dual–monoclonal antibody sandwich immunoassay to measure hepcidin-25 in patients (a) during initiation of in vitro fertilization when endogenous estrogens were elevated vs. suppressed, (b) with GH deficiency before and after 12 months substitution treatment, (c) with hyperthyroidism before and after normalization, and (d) with hyperprolactinemia before and after six months of treatment with a dopamine agonist. Results In response to a marked stimulation of endogenous estrogen production, median hepcidin levels decreased from 4.85 to 1.43 ng/mL (p < 0.01). Hyperthyroidism, hyperprolactinemia, or GH substitution to GH-deficient patients did not influence serum hepcidin-25 levels. Conclusions In humans, gonadotropin-stimulated endogenous estrogen markedly decreases circulating hepcidin-25 levels. No clear and stable correlation between iron biomarkers and hepcidin-25 was seen before or after treatment of hyperthyroidism, hyperprolactinemia or growth hormone deficiency. PMID:26866603

Stability and superconducting properties of GaH5 at high pressure

NASA Astrophysics Data System (ADS)

Ning, Yan-Li; Yang, Wen-Hua; Zang, Qing-Jun; Lu, Wen-Cai

2017-11-01

Using genetic algorithm (GA) method combined with first-principles calculations, the structures, dynamical and thermodynamic stabilities of GaH5 were studied. The calculated results suggested that at the pressure range 150-400 GPa, the P21/m phase of GaH5 is the most favorable phase and dynamically stable, but thermodynamically it is unstable and can decompose into GaH3 and H2. The superconducting property of GaH5 was further calculated, and the predicted superconducting transformation temperature Tc of GaH5 P21/m phase is about 35.63 K at 250 GPa. Besides, we compared the GaH5 and GaH3 superconducting properties, and found that GaH3-Pm-3n structure has a larger DOS near Fermi level than GaH5-P21/m structure, which may be the main reason causing higher Tc of GaH3 than GaH5.

Spin injection in epitaxial MnGa(111)/GaN(0001) heterostructures

NASA Astrophysics Data System (ADS)

Zube, Christian; Malindretos, Joerg; Watschke, Lars; Zamani, Reza R.; Disterheft, David; Ulbrich, Rainer G.; Rizzi, Angela; Iza, Michael; Keller, Stacia; DenBaars, Steven P.

2018-01-01

Ferromagnetic MnGa(111) layers were grown on GaN(0001) by molecular beam epitaxy. MnGa/GaN Schottky diodes with a doping level of around n = 7 × 1018 cm-3 were fabricated to achieve single step tunneling across the metal/semiconductor junction. Below the GaN layer, a thin InGaN quantum well served as optical spin detector ("spin-LED"). For electron spin injection from MnGa into GaN and subsequent spin transport through a 45 nm (70 nm) thick GaN layer, we observe a circular polarization of 0.3% (0.2%) in the electroluminescence at 80 K. Interface mixing, spin polarization losses during electrical transport in the GaN layer, and spin relaxation in the InGaN quantum well are discussed in relation with the low value of the optically detected spin polarization.

Role of Endogenous Cholecystokinin on Growth of Human Pancreatic Cancer

PubMed Central

Matters, Gail L.; McGovern, Christopher; Harms, John F.; Markovic, Kevin; Anson, Krystal; Jayakumar, Calpurnia; Martenis, Melissa; Awad, Christina; Smith, Jill P.

2012-01-01

Cholecystokinin (CCK) and gastrin stimulate growth of pancreatic cancer. Although down regulation of gastrin inhibits growth of pancreatic cancer, the contribution of endogenous CCK to tumor growth is unknown. The purpose of this study was to evaluate the role of endogenous CCK on autocrine growth of pancreatic cancer. Pancreatic cancer cell lines were analyzed for CCK mRNA and peptide expression by real time RT-PCR and radioimmunoassay, respectively. The effect of endogenous CCK on growth was evaluated by treating cancer cells with CCK neutralizing antibodies and by down regulating CCK mRNA by RNAi. Wild type pancreatic cancer cells expressed significantly lower CCK mRNA and peptide levels than gastrin. Neither treatment of pancreatic cancer cells with CCK antibodies nor the down regulation of CCK mRNA and peptide by shRNAs altered growth in vitro or in vivo. Conversely, when gastrin mRNA expression was down regulated, the same cells failed to produce tumors in spite of having sustained levels of endogenous CCK. Pancreatic cancer cells produce CCK and gastrin; however, the autocrine production of gastrin is more important for stimulating tumor growth. PMID:21186400

Brain regions involved in the development of acute phase responses accompanying fever in rabbits.

PubMed Central

Morimoto, A; Murakami, N; Nakamori, T; Sakata, Y; Watanabe, T

1989-01-01

1. The effects of microinjection of rabbit endogenous pyrogen and human recombinant interleukin-1 alpha on rectal temperature and acute phase responses were extensively examined in forty different brain regions of rabbits. The acute phase responses that were investigated were the changes in plasma levels of iron, zinc and copper concentration and the changes in circulating leucocyte count. 2. The rostral hypothalamic regions, such as nucleus broca ventralis, preoptic area and anterior hypothalamic region, responded to the microinjection of endogenous pyrogen or interleukin-1 by producing both fever and acute phase responses. 3. The microinjection of endogenous pyrogen or interleukin-1 into the rostral hypothalamic regions significantly decreased the plasma levels of iron and zinc concentration 8 and 24 h after injection. The circulating leucocyte count increased 8 h after injection. However, neither the injections of endogenous pyrogen nor interleukin-1 affected the number of red blood cells. 4. The present results show that the rostral hypothalamic regions respond directly to endogenous pyrogen or interleukin-1 with the consequent development of fever and acute phase responses. PMID:2514261

Gibberellin (GA3) enhances cell wall invertase activity and mRNA levels in elongating dwarf pea (Pisum sativum) shoots

NASA Technical Reports Server (NTRS)

Wu, L. L.; Mitchell, J. P.; Cohn, N. S.; Kaufman, P. B.

1993-01-01

The invertase (EC 3.2.1.26) purified from cell walls of dwarf pea stems to homogeneity has a molecular mass of 64 kilodaltons (kD). Poly(A)+RNA was isolated from shoots of dwarf pea plants, and a cDNA library was constructed using lambda gt11 as an expression vector. The expression cDNA library was screened with polyclonal antibodies against pea cell wall invertase. One invertase cDNA clone was characterized as a full-length cDNA with 1,863 base pairs. Compared with other known invertases, one homologous region in the amino acid sequence was found. The conserved motif, Asn-Asp-Pro-Asn-Gly, is located near the N-terminal end of invertase. Northern blot analysis showed that the amount of invertase mRNA (1.86 kb) was rapidly induced to a maximal level 4 h after GA3 treatment, then gradually decreased to the control level. The mRNA level at 4 h in GA3-treated peas was fivefold higher than that of the control group. The maximal increase in activity of pea cell wall invertase elicited by GA3 occcured at 8 h after GA3 treatment. This invertase isoform was shown immunocytochemically to be localized in the cell walls, where a 10-fold higher accumulation occurred in GA3-treated tissue compared with control tissue. This study indicates that the expression of the pea shoot cell-wall invertase gene could be regulated by GA3 at transcriptional and/or translational levels.

Positron Annihilation Induced Auger Electron Spectroscopic Studies Of Reconstructed Semiconductor Surfaces

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Reed, J. A.; Starnes, S. G.; Weiss, A. H.

2011-06-01

The positron annihilation induced Auger spectrum from GaAs(100) displays six As and three Ga Auger peaks below 110 eV corresponding to M4,5VV, M2M4V, M2,3M4,5M4,5 Auger transitions for As and M2,3M4,5M4,5 Auger transitions for Ga. The integrated Auger peak intensities have been used to obtain experimental annihilation probabilities of surface trapped positrons with As 3p and 3d and Ga 3p core level electrons. PAES data is analyzed by performing calculations of positron surface and bulk states and annihilation characteristics of surface trapped positrons with relevant Ga and As core level electrons for both Ga- and As-rich (100) surfaces of GaAs, ideally terminated, non-reconstructed and with (2×8), (2×4), and (4×4) reconstructions. The orientation-dependent variations of the atomic and electron densities associated with reconstructions are found to affect localization of the positron wave function at the surface. Computed positron binding energy, work function, and annihilation characteristics demonstrate their sensitivity both to chemical composition and atomic structure of the topmost layers of the surface. Theoretical annihilation probabilities of surface trapped positrons with As 3d, 3p, and Ga 3p core level electrons are compared with the ones estimated from the measured Auger peak intensities.

Investigation of Defect Distributions in SiO2/AlGaN/GaN High-Electron-Mobility Transistors by Using Capacitance-Voltage Measurement with Resonant Optical Excitation

NASA Astrophysics Data System (ADS)

Kim, Tae-Soo; Lim, Seung-Young; Park, Yong-Keun; Jung, Gunwoo; Song, Jung-Hoon; Cha, Ho-Young; Han, Sang-Woo

2018-06-01

We investigated the distributions and the energy levels of defects in SiO2/AlGaN/GaN highelectron-mobility transistors (HEMTs) by using frequency-dependent ( F- D) capacitance-voltage ( C- V) measurements with resonant optical excitation. A Schottky barrier (SB) and a metal-oxidesemiconductor (MOS) HEMT were prepared to compare the effects of defects in their respective layers. We also investigated the effects of those layers on the threshold voltage ( V th ). A drastic voltage shift in the C- V curve at higher frequencies was caused by the large number of defect levels in the SiO2/GaN interface. A significant shift in V th with additional light illumination was observed due to a charging of the defect states in the SiO2/GaN interface. The voltage shifts were attributed to the detrapping of defect states at the SiO2/GaN interface.

Antagonism between abscisic acid and gibberellins is partially mediated by ascorbic acid during seed germination in rice.

PubMed

Ye, Nenghui; Zhang, Jianhua

2012-05-01

The antagonism between abscisic acid (ABA) and gibberellin (GA) plays a key role in controlling seed germination, but the mechanism of antagonism during this process is not known. In the associated study, we investigated the relationship among ABA, reactive oxygen species (ROS), ascorbic acid (ASC) and GA during rice seed germination. ROS production is reduced by ABA, which hence results in decreasing ASC accumulation during imbibition. GA accumulation was also suppressed by a reduced ROS and ASC level, whereas application of exogenous ASC can partially rescue seed germination from ABA treatment. Further results show that production of ASC, which acts as a substrate in GA biosynthesis, was significantly inhibited by lycorine which thus suppressed the accumulation of GA. Consequently, expression of GA biosynthesis genes was suppressed by the low levels of ROS and ASC in ABA-treated seeds. These studies reveal a new role for ASC in mediating the antagonism between ABA and GA during seed germination in rice.

Graphene/h-BN/GaAs sandwich diode as solar cell and photodetector.

PubMed

Li, Xiaoqiang; Lin, Shisheng; Lin, Xing; Xu, Zhijuan; Wang, Peng; Zhang, Shengjiao; Zhong, Huikai; Xu, Wenli; Wu, Zhiqian; Fang, Wei

2016-01-11

In graphene/semiconductor heterojunction, the statistic charge transfer between graphene and semiconductor leads to decreased junction barrier height and limits the Fermi level tuning effect in graphene, which greatly affects the final performance of the device. In this work, we have designed a sandwich diode for solar cells and photodetectors through inserting 2D hexagonal boron nitride (h-BN) into graphene/GaAs heterostructure to suppress the static charge transfer. The barrier height of graphene/GaAs heterojunction can be increased from 0.88 eV to 1.02 eV by inserting h-BN. Based on the enhanced Fermi level tuning effect with interface h-BN, through adopting photo-induced doping into the device, power conversion efficiency (PCE) of 10.18% has been achieved for graphene/h-BN/GaAs compared with 8.63% of graphene/GaAs structure. The performance of graphene/h-BN/GaAs based photodetector is also improved with on/off ratio increased by one magnitude compared with graphene/GaAs structure.

Invasive fungal infections in endogenous Cushing's syndrome

PubMed Central

Scheffel, Rafael Selbach; Dora, José Miguel; Weinert, Letícia Schwerz; Aquino, Valério; Maia, Ana Luiza; Canani, Luis Henrique; Goldani, Luciano Z.

2010-01-01

Cushing's syndrome is a condition characterized by elevated cortisol levels that can result from either augmented endogenous production or exogenous administration of corticosteroids. The predisposition to fungal infections among patients with hypercortisolemia has been noted since Cushing's original description of the disease. We describe here a patient with endogenous Cushing's syndrome secondary to an adrenocortical carcinoma, who developed concomitant disseminated cryptococcosis and candidiasis in the course of his disease. PMID:24470886

Terahertz photoluminescence from S.I.-GaAs by below gap excitation via EL2 level

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oyama, Yutaka, E-mail: oyama@material.tohoku.ac.jp; Dezaki, Hikari; Shimizu, Yusaku

2015-01-12

Terahertz emission by radiative transitions in semi-conductors via shallow impurity states is investigated. We report on the observation of terahertz photoluminescence from S.I.-GaAs by below gap excitation via EL2 level which is located at the center of band gap. In order to investigate the terahertz wave emission mechanisms, the emission spectra and temperature dependence of the emission intensity are evaluated. It is shown that intense terahertz emission from S.I.-GaAs over 120 K is observed due to the thermal recovery of photo-quenched EL2 meta-stable state, and that the emission peak frequency looks to be attributed to the shallow level energy in GaAs.

Defect and interface analyses of non-stoichiometric n-type GaSb thin films grown on Ge(100) substrates by rapid thermal annealing

NASA Astrophysics Data System (ADS)

Nishimoto, Naoki; Fujihara, Junko; Yoshino, Katsumi

2018-05-01

In this study, Ga0.6Sb0.4 thin films were grown on quartz and Ge(100) 1° off-axis substrates by RF magnetron sputtering at 500 °C. Ga0.6Sb0.4/Ge(100) shows n-type conductivity at room temperature (RT) and p-type conductivity at low temperatures, whereas undoped GaSb thin films exhibit p-type conductivity, irrespective of their growth methods and conditions. Their electrical properties were determined by rapid thermal annealing, which revealed that Ga0.6Sb0.4/Ge(100) contains two types of acceptors and two types of donors. The acceptors are considered to be GaSb and electrically active sites on dislocations originating at the Ga0.6Sb0.4/Ge(100) interface, while donors are believed to be Gai and electrically active sites originating at the Ga0.6Sb0.4/Ge(100) interface. In these acceptors and donors, the shallow donor concentration is higher than the shallow acceptor concentration, and the shallow donor level is deeper than the shallow acceptor level. Thus, we concluded that Ga0.6Sb0.4/Ge(100) shows n-type conductivity at RT due to electrically active sites originating at the Ga0.6Sb0.4/Ge(100) interface and native defects originating from excess Ga.

Low- and high-testosterone individuals exhibit decreased aversion to economic risk.

PubMed

Stanton, Steven J; Mullette-Gillman, O'Dhaniel A; McLaurin, R Edward; Kuhn, Cynthia M; LaBar, Kevin S; Platt, Michael L; Huettel, Scott A

2011-04-01

Testosterone is positively associated with risk-taking behavior in social domains (e.g., crime, physical aggression). However, the scant research linking testosterone to economic risk preferences presents inconsistent findings. We examined the relationship between endogenous testosterone and individuals' economic preferences (i.e., risk preference, ambiguity preference, and loss aversion) in a large sample (N = 298) of men and women. We found that endogenous testosterone levels have a significant U-shaped association with individuals' risk and ambiguity preferences, but not loss aversion. Specifically, individuals with low or high levels of testosterone (more than 1.5 SD from the mean for their gender) were risk and ambiguity neutral, whereas individuals with intermediate levels of testosterone were risk and ambiguity averse. This relationship was highly similar in men and women. In contrast to received wisdom regarding testosterone and risk, the present data provide the first robust evidence for a nonlinear association between economic preferences and levels of endogenous testosterone.

Effects of moist cold stratification on germination, plant growth regulators, metabolites and embryo ultrastructure in seeds of Acer morrisonense (Sapindaceae).

PubMed

Chen, Shun-Ying; Chou, Shih-Han; Tsai, Ching-Chu; Hsu, Wen-Yu; Baskin, Carol C; Baskin, Jerry M; Chien, Ching-Te; Kuo-Huang, Ling-Long

2015-09-01

Breaking of seed dormancy by moist cold stratification involves complex interactions in cells. To assess the effect of moist cold stratification on dormancy break in seeds of Acer morrisonense, we monitored percentages and rates of germination and changes in plant growth regulators, sugars, amino acids and embryo ultrastructure after various periods of cold stratification. Fresh seeds incubated at 25/15 °C for 24 weeks germinated to 61%, while those cold stratified at 5 °C for 12 weeks germinated to 87% in 1 week. Neither exogenous GA3 nor GA4 pretreatment significantly increased final seed germination percentage. Total ABA content of seeds cold stratified for 12 weeks was reduced about 3.3-fold, to a concentration similar to that in germinated seeds (radicle emergence). Endogenous GA3 and GA7 were detected in 8-week and 12-week cold stratified seeds but not in fresh seeds. Numerous protein and lipid bodies were present in the plumule, first true leaves and cotyledons of fresh seeds. Protein and lipid bodies decreased greatly during cold stratification, and concentrations of total soluble sugars and amino acids increased. The major non-polar sugars in fresh seeds were sucrose and fructose, but sucrose increased and fructose decreased significantly during cold stratification. The major free amino acids were proline and tryptophan in fresh seeds, and proline increased and tryptophan decreased during cold stratification. Thus, as dormancy break occurs during cold stratification seeds of A. morrisonense undergo changes in plant growth regulators, proteins, lipids, sugars, amino acids and cell ultrastructure. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Rice PLASTOCHRON genes regulate leaf maturation downstream of the gibberellin signal transduction pathway.

PubMed

Mimura, Manaki; Nagato, Yasuo; Itoh, Jun-Ichi

2012-05-01

Rice PLASTOCHRON 1 (PLA1) and PLA2 genes regulate leaf maturation and plastochron, and their loss-of-function mutants exhibit small organs and rapid leaf emergence. They encode a cytochrome P450 protein CYP78A11 and an RNA-binding protein, respectively. Their homologs in Arabidopsis and maize are also associated with plant development/organ size. Despite the importance of PLA genes in plant development, their molecular functions remain unknown. Here, we investigated how PLA1 and PLA2 genes are related to phytohormones. We found that gibberellin (GA) is the major phytohormone that promotes PLA1 and PLA2 expression. GA induced PLA1 and PLA2 expression, and conversely the GA-inhibitor uniconazole suppressed PLA1 and PLA2 expression. In pla1-4 and pla2-1 seedlings, expression levels of GA biosynthesis genes and the signal transduction gene were similar to those in wild-type seedlings. GA treatment slightly down-regulated the GA biosynthesis gene GA20ox2 and up-regulated the GA-catabolizing gene GA2ox4, whereas the GA biosynthesis inhibitor uniconazole up-regulated GA20ox2 and down-regulated GA2ox4 both in wild-type and pla mutants, suggesting that the GA feedback mechanism is not impaired in pla1 and pla2. To reveal how GA signal transduction affects the expression of PLA1 and PLA2, PLA expression in GA-signaling mutants was examined. In GA-insensitive mutant, gid1 and less-sensitive mutant, Slr1-d1, PLA1 and PLA2 expression was down-regulated. On the other hand, the expression levels of PLA1 and PLA2 were highly enhanced in a GA-constitutive-active mutant, slr1-1, causing ectopic overexpression. These results indicate that both PLA1 and PLA2 act downstream of the GA signal transduction pathway to regulate leaf development.

Vacancy Defects as Compensating Centers in Mg-Doped GaN

NASA Astrophysics Data System (ADS)

Hautakangas, S.; Oila, J.; Alatalo, M.; Saarinen, K.; Liszkay, L.; Seghier, D.; Gislason, H. P.

2003-04-01

We apply positron annihilation spectroscopy to identify VN-MgGa complexes as native defects in Mg-doped GaN. These defects dissociate in postgrowth annealings at 500 800 °C. We conclude that VN-MgGa complexes contribute to the electrical compensation of Mg as well as the activation of p-type conductivity in the annealing. The observation of VN-MgGa complexes confirms that vacancy defects in either the N or Ga sublattice are abundant in GaN at any position of the Fermi level during growth, as predicted previously by theoretical calculations.

On the optical evaluation of the EL2 deep level concentration in semi-insulating GaAs

NASA Technical Reports Server (NTRS)

Walukiewicz, W.; Lagowski, J.; Gatos, H. C.

1983-01-01

A practical procedure for the evaluation of the Fermi energy in semi-insulating (SI)GaAs from electrical measurements is presented. This procedure makes it possible to reliably extend the determination of the major deep level (EL2) concentration, by near-infrared absorption measurements, to SIGaAs. Employing this procedure, it is shown that the EL2 concentration in Czochralski-grown GaAs increases monotonically with increasing As/Ga ratio (throughout the conversion from SI n type to semiconducting p-type crystals) rather than abruptly as previously proposed.

Low-temperature photoluminescence study of thin epitaxial GaAs films on Ge substrates

NASA Astrophysics Data System (ADS)

Brammertz, Guy; Mols, Yves; Degroote, Stefan; Motsnyi, Vasyl; Leys, Maarten; Borghs, Gustaaf; Caymax, Matty

2006-05-01

Thin epitaxial GaAs films, with thickness varying from 140 to 1000 nm and different Si doping levels, were grown at 650 °C by organometallic vapor phase epitaxy on Ge substrates and analyzed by low-temperature photoluminescence (PL) spectroscopy. All spectra of thin GaAs on Ge show two different structures, one narrow band-to-band (B2B) structure at an energy of ~1.5 eV and a broad inner-band-gap (IB) structure at an energy of ~1.1 eV. Small strain in the thin GaAs films causes the B2B structure to be separated into a light-hole and a heavy-hole peak. At 2.5 K the good structural quality of the thin GaAs films on Ge can be observed from the narrow excitonic peaks. Peak widths of less than 1 meV are measured. GaAs films with thickness smaller than 200 nm show B2B PL spectra with characteristics of an n-type doping level of approximately 1018 at./cm3. This is caused by heavy Ge diffusion from the substrate into the GaAs at the heterointerface between the two materials. The IB structure observed in all films consists of two Gaussian peaks with energies of 1.04 and 1.17 eV. These deep trapping states arise from Ge-based complexes formed within the GaAs at the Ge-GaAs heterointerface, due to strong diffusion of Ge atoms into the GaAs. Because of similarities with Si-based complexes, the peak at 1.04 eV was identified to be due to a GeGa-GeAs complex, whereas the peak at 1.17 eV was attributed to the GeGa-VGa complex. The intensity of the IB structure decreases strongly as the GaAs film thickness is increased. PL intensity of undoped GaAs films containing antiphase domains (APDs) is four orders of magnitude lower than for similar films without APDs. This reduction in intensity is due to the electrically active Ga-Ga and As-As bonds at the boundaries between the different APDs. When the Si doping level is increased, the PL intensity of the APD-containing films is increased again as well. A film containing APDs with a Si doping level of ~1018 at./cm3 has only a factor 10 reduced intensity. We tentatively explain this observation by Si or Ge clustering at antiphase boundaries, which eliminates the effects of the Ga-Ga and As-As bonds. This assumption is confirmed by the fact that, at 77 K, the ratio between the intensity of the IB peak at 1.17 eV to the intensity of the peak at 1.04 eV is smaller than 1.4 for all films containing APDs, whereas it is larger than 1.4 for all films without APDs. This shows stronger clustering of Si or Ge in the material with APDs. For future electronic applications, Ge diffusion into the GaAs will have to be reduced. PL analysis will be a rapid tool for studying the Ge diffusion into the GaAs thin films.

Isolation and Role of PmRGL2 in GA-mediated Floral Bud Dormancy Release in Japanese Apricot (Prunus mume Siebold et Zucc.)

PubMed Central

Lv, Lin; Huo, Ximei; Wen, Luhua; Gao, Zhihong; Khalil-ur-Rehman, Muhammad

2018-01-01

Bud dormancy release is regulated by gibberellins (GAs). DELLA proteins are highly conserved and act as negative regulators in GA signaling pathway. The present study established a relationship between PmRGL2 in Japanese apricot and GA4 levels during dormancy release of floral buds. Overexpression of PmRGL2 in poplar delayed the onset of bud dormancy and resulted in dwarf plants, relative to wild-type trees. PmRGL2 exhibited higher expression during ecodormancy and relatively lower expression during endodormancy. The relative level of GA4 exhibited an increasing trend at the transition from endodormancy to ecodormancy and displayed a similar expression pattern of genes related to GA metabolism, PmGA20ox2, PmGA3ox1, PmGID1b, in both Japanese apricot and transgenic poplar. These results suggests that PmRGL2 acts as an integrator and negative regulator of dormancy via a GA-signaling pathway. Moreover, an interaction between RGL2 and SLY1 in a yeast two hybrid (Y2H) system further suggests that SCF E3 ubiquitin ligases, such as SLY1, may be a critical factor in the regulation of RGL2 through an SCFSLY1-proteasome pathway. Our study demonstrated that PmRGL2 plays a negative role in bud dormancy release by regulating the GA biosynthetic enzymes, GA20ox and GA3ox1 and the GA receptor, GID1b. PMID:29434610

Gastrin levels in mothers and neonates at delivery in various perinatal conditions.

PubMed

Morán, C; Carranza-Lira, S; Ochoa, R; Martínez, J C; Herrera, M; Fonseca, E; Zárate, A

1996-08-01

This study was designed to assess the variations of gastrin (Ga) serum levels in mothers and newborns at birth in some perinatal disorders. Ga levels were measured by RIA in maternal serum, amniotic fluid and cord sera of newborns in 55 cases with the following conditions: normal pregnancy and eutocic vaginal delivery (n = 8), repeat cesarean section (n = 10), and cardiotogographic register suggestive of fetal compromise (n = 15), cephalopelvic disproportion (n = 8), preeclampsia (n = 7) and postdate pregnancy (n = 7). Statistical analysis was performed by Mann-Whitney U test. Ga levels in cord sera of newborn and amniotic fluid in normal pregnancy and eutocic delivery were significantly higher (p < 0.02 and p < 0.01, respectively) than those found in patients with repeat cesarean operation. Serum Ga concentrations in women with postterm pregnancy were significantly higher (p < 0.02) than in women with prior cesarean section. Ga levels in amniotic fluid samples in the presence of suspected fetal compromise and postdate pregnancy were significantly higher (p < 0.001) than those observed in women who had repeat cesarean operation. Vaginal delivery and perinatal pathology may induce hypergastrinemia in both mother and neonate at birth.

Polymorphism in beta fibrinogen -455 g/a gene was associated with diabetic in severe ischemic stroke patients

NASA Astrophysics Data System (ADS)

Ritarwan, Kiking; Kadri, Alfansuri; Juwita Sembiring, Rosita

2018-03-01

There is a association of polymorphism in the promoter region of the beta fibrinogen gene -455 G/A with enhancement plasma fibrinogen level. Diabetes mellitus is a risk factor for early neurologic deterioration in acute ischemic stroke. The prothrombotic fibrinogen protein is frequently elevated in patients with diabetes and may be association with poorer prognosis. This study evaluated the association of beta fibrinogen gene -455 G/A promoter polymorphism on modified Ranking Scale of Ischemic Stroke patients treated with diabetic and nondiabetic group. In a Cohort study design comprises 200 consecutive patients diabetic and a nondiabetic who, three months using completed a detailed outcome stroke. Of 200 samples genotype distribution were 27.1% for GG+GA and 0% for AA with diabetic and than 4.4% for GG+GA and 0.05% diabetic patients. Fibrinogen levels were higher in diabetic than nondiabetic group patients (307.7 + 106.3 vs 278 + 84 gr/dl, p=0.002). Fibrinogen level was found to be an independent predictor for diabetic patients. On Genotype GG+GA were associated wth diabetic and nondiabetic group patients. Modified Rankin Scale on day 90 were found associated with diabetic and nondiabetic patients. Conclusion: Elevated fibrinogen level is dose-dependently associated with 90 days outcome severity stroke with diabetic following ischemic stroke

Band bending at the heterointerface of GaAs/InAs core/shell nanowires monitored by synchrotron X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Khanbabaee, B.; Bussone, G.; Knutsson, J. V.; Geijselaers, I.; Pryor, C. E.; Rieger, T.; Demarina, N.; Grützmacher, D.; Lepsa, M. I.; Timm, R.; Pietsch, U.

2016-10-01

Unique electronic properties of semiconductor heterostructured nanowires make them useful for future nano-electronic devices. Here, we present a study of the band bending effect at the heterointerface of GaAs/InAs core/shell nanowires by means of synchrotron based X-ray photoelectron spectroscopy. Different Ga, In, and As core-levels of the nanowire constituents have been monitored prior to and after cleaning from native oxides. The cleaning process mainly affected the As-oxides and was accompanied by an energy shift of the core-level spectra towards lower binding energy, suggesting that the As-oxides turn the nanowire surfaces to n-type. After cleaning, both As and Ga core-levels revealed an energy shift of about -0.3 eV for core/shell compared to core reference nanowires. With respect to depth dependence and in agreement with calculated strain distribution and electron quantum confinement, the observed energy shift is interpreted by band bending of core-levels at the heterointerface between the GaAs nanowire core and the InAs shell.

Study of GaAs-oxide interface by transient capacitance spectroscopy - Discrete energy interface states

NASA Technical Reports Server (NTRS)

Kamieniecki, E.; Kazior, T. E.; Lagowski, J.; Gatos, H. C.

1980-01-01

Interface states and bulk GaAs energy levels were simultaneously investigated in GaAs MOS structures prepared by anodic oxidation. These two types of energy levels were successfully distinguished by carrying out a comparative analysis of deep level transient capacitance spectra of the MOS structures and MS structures prepared on the same samples of epitaxially grown GaAs. The identification and study of the interface states and bulk levels was also performed by investigating the transient capacitance spectra as a function of the filling pulse magnitude. It was found that in the GaAs-anodic oxide interface there are states present with a discrete energy rather than with a continuous energy distribution. The value of the capture cross section of the interface states was found to be 10 to the 14th to 10 to the 15th/sq cm, which is more accurate than the extremely large values of 10 to the -8th to 10 to the -9th/sq cm reported on the basis of conductance measurements.

CLD (chronic liver diseases)-HbA1C as a suitable indicator for estimation of mean plasma glucose in patients with chronic liver diseases.

PubMed

Koga, Masafumi; Kasayama, Soji; Kanehara, Hideo; Bando, Yukihiro

2008-08-01

In patients with chronic liver diseases (CLD), turnover of erythrocytes is increased whereas that of serum albumin is decreased. Thus, glycated hemoglobin (HbA(1C)) and glycated albumin (GA) cannot be used as adequate indicators for chronic plasma glucose control in diabetic patients with CLD. In this investigation, we have proposed CLD-HbA(1C), a novel long-term glycemic control marker by using measured HbA(1C) and GA. We studied 82 patients with CLD in whom glycemic control was regarded as to be stable. Daily plasma glucose profiles were monitored and estimated levels of HbA(1C) were calculated on the conversion formula established by Rohlfing et al. [C.L. Rohlfing, J.D. England, H.M. Wiedmeyer, A. Tennill, R.R. Little, D.E. Goldstein, Defining the relationship between plasma glucose and HbA1c, Diabetes Care 25 (2002) 275-278]. Cholinesterase (ChE) as an indicator for hepatic function was determined at the same time when HbA(1C) and GA levels were measured. CLD-HbA(1C) was defined as the average of measured HbA(1C) and GA/3, based upon the results that among healthy individuals, GA levels were roughly estimated at approximately threefold higher than HbA(1C) levels. While measured HbA(1C) levels in patients with CLD were generally lower than estimated HbA(1C) levels, GA/3 values were generally higher than estimated HbA(1C) levels. Such discrepancies lineally increased in accordance with a decrease in ChE levels. On the other hand, CLD-HbA(1C) levels were highly correlated with estimated HbA(1C) levels (R=0.883), while no significant correlation between CLD-HbA(1C) and ChE was noted. In conclusion, CLD-HbA(1C) has been found a superior chronic glycemic control marker than HbA(1C) or GA in diabetic patients with chronic liver diseases.

Lifting DELLA Repression of Arabidopsis Seed Germination by Nonproteolytic Gibberellin Signaling1[C][W][OPEN

PubMed Central

Ariizumi, Tohru; Hauvermale, Amber L.; Nelson, Sven K.; Hanada, Atsushi; Yamaguchi, Shinjiro; Steber, Camille M.

2013-01-01

DELLA repression of Arabidopsis (Arabidopsis thaliana) seed germination can be lifted either through DELLA proteolysis by the ubiquitin-proteasome pathway or through proteolysis-independent gibberellin (GA) hormone signaling. GA binding to the GIBBERELLIN-INSENSITIVE DWARF1 (GID1) GA receptors stimulates GID1-GA-DELLA complex formation, which in turn triggers DELLA protein ubiquitination and proteolysis via the SCFSLY1 E3 ubiquitin ligase and 26S proteasome. Although DELLA cannot be destroyed in the sleepy1-2 (sly1-2) F-box mutant, long dry after-ripening and GID1 overexpression can relieve the strong sly1-2 seed dormancy phenotype. It appears that sly1-2 seed dormancy results from abscisic acid (ABA) signaling downstream of DELLA, since dormant sly1-2 seeds accumulate high levels of ABA hormone and loss of ABA sensitivity rescues sly1-2 seed germination. DELLA positively regulates the expression of XERICO, an inducer of ABA biosynthesis. GID1b overexpression rescues sly1-2 germination through proteolysis-independent DELLA down-regulation associated with increased expression of GA-inducible genes and decreased ABA accumulation, apparently as a result of decreased XERICO messenger RNA levels. Higher levels of GID1 overexpression are associated with more efficient sly1 germination and increased GID1-GA-DELLA complex formation, suggesting that GID1 down-regulates DELLA through protein binding. After-ripening results in increased GA accumulation and GID1a-dependent GA signaling, suggesting that after-ripening triggers GA-stimulated GID1-GA-DELLA protein complex formation, which in turn blocks DELLA transcriptional activation of the XERICO inhibitor of seed germination. PMID:23818171

E+ Transition in GaAs1-xNx and GaAs1-xBix Due to Isoelectronic-Impurity-Induced Perturbation of the Conduction Band

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fluegel, B.; Mascarenhas, A.; Ptak, A. J.

2007-01-01

An above-band-gap transition E{sub +} is experimentally observed in the dilute GaAs{sub 1-x}Bi{sub x} alloy. Precise measurements at very low dilutions are made of the above-band-gap transition E{sub +} that is observed in GaAs{sub 1-x}N{sub x}, making it possible to compare the behavior of the different isoelectronic traps Bi and N in the common host GaAs with respect to their perturbation to the host electronic structure. We suggest that the origin of the E{sub +} level observed in GaAs is not the isolated isoelectronic impurity level N{sub x}, as is presumed in the band-anticrossing model, but rather the isoelectronic-impurity-induced perturbationmore » of the conduction band L{sub 6}{sup c}.« less

Record-level quantum efficiency from a high polarization strained GaAs/GaAsP superlattice photocathode with distributed Bragg reflector

DOE PAGES

Liu, Wei; Chen, Yiqiao; Lu, Wentao; ...

2016-12-19

Photocathodes that provide high polarization and high quantum efficiency (QE) can significantly enhance the physics capabilities of electron accelerators. We report record-level QE from a high-polarization strained GaAs/GaAsP superlattice photocathode fabricated with a Distributed Bragg Reflector (DBR). The DBR photocathode technique enhances the absorption of incident laser light thereby enhancing QE, but as literature suggests, it is very challenging to optimize all of the parameters associated with the fabrication of complicated photocathode structures composed of many distinct layers. Past reports of DBR photocathodes describe high polarization but typically QE of only ~ 1%, which is comparable to QE of highmore » polarization photocathodes grown without a DBR structure. As a result, this work describes a new strained GaAs/GaAsP superlattice DBR photocathode exhibiting polarization of 84% and QE of 6.4%.« less

Record-level quantum efficiency from a high polarization strained GaAs/GaAsP superlattice photocathode with distributed Bragg reflector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wei; Chen, Yiqiao; Lu, Wentao

Photocathodes that provide high polarization and high quantum efficiency (QE) can significantly enhance the physics capabilities of electron accelerators. We report record-level QE from a high-polarization strained GaAs/GaAsP superlattice photocathode fabricated with a Distributed Bragg Reflector (DBR). The DBR photocathode technique enhances the absorption of incident laser light thereby enhancing QE, but as literature suggests, it is very challenging to optimize all of the parameters associated with the fabrication of complicated photocathode structures composed of many distinct layers. Past reports of DBR photocathodes describe high polarization but typically QE of only ~ 1%, which is comparable to QE of highmore » polarization photocathodes grown without a DBR structure. As a result, this work describes a new strained GaAs/GaAsP superlattice DBR photocathode exhibiting polarization of 84% and QE of 6.4%.« less

Selective Amperometric Recording of Endogenous Ascorbate Secretion from a Single Rat Adrenal Chromaffin Cell with Pretreated Carbon Fiber Microelectrodes.

PubMed

Wang, Kai; Xiao, Tongfang; Yue, Qingwei; Wu, Fei; Yu, Ping; Mao, Lanqun

2017-09-05

Quantitative description of ascorbate secretion at a single-cell level is of great importance in physiological studies; however, most studies on the ascorbate secretion have so far been performed through analyzing cell extracts with high performance liquid chromatography, which lacks time resolution and analytical performance on a single-cell level. This study demonstrates a single-cell amperometry with carbon fiber microelectrodes (CFEs) to selectively monitor amperometric vesicular secretion of endogenous ascorbate from a single rat adrenal chromaffin cell. The CFEs are electrochemically pretreated in a weakly basic solution (pH 9.5), and such pretreatment essentially enables the oxidation of ascorbate to occur at a relatively low potential (i.e., 0.0 V vs Ag/AgCl), and further a high selectivity for ascorbate measurement over endogenously existing electroactive species such as epinephrine, norepinephrine, and dopamine. The selectivity is ensured by much larger amperometric response at the pretreated CFEs toward ascorbate over those toward other endogenously existing electroactive species added into the solution or ejected to the electrode with a micropuffer pipet, and by the totally suppressed current response by adding ascorbate oxidase into the cell lysate. With the pretreated CFE-based single-cell amperometry developed here, exocytosis of endogenous ascorbate of rat adrenal chromaffin cells is directly observed and ensured with the calcium ion-dependent high K + -induced secretion of endogenous ascorbate from the cells. Moreover, the quantitative information on the exocytosis of endogenous ascorbate is provided.

Endogenous lycopene improves ethanol production under acetic acid stress in Saccharomyces cerevisiae.

PubMed

Pan, Shuo; Jia, Bin; Liu, Hong; Wang, Zhen; Chai, Meng-Zhe; Ding, Ming-Zhu; Zhou, Xiao; Li, Xia; Li, Chun; Li, Bing-Zhi; Yuan, Ying-Jin

2018-01-01

Acetic acid, generated from the pretreatment of lignocellulosic biomass, is a significant obstacle for lignocellulosic ethanol production. Reactive oxidative species (ROS)-mediated cell damage is one of important issues caused by acetic acid. It has been reported that decreasing ROS level can improve the acetic acid tolerance of Saccharomyces cerevisiae . Lycopene is known as an antioxidant. In the study, we investigated effects of endogenous lycopene on cell growth and ethanol production of S. cerevisiae in acetic acid media. By accumulating endogenous lycopene during the aerobic fermentation of the seed stage, the intracellular ROS level of strain decreased to 1.4% of that of the control strain during ethanol fermentation. In the ethanol fermentation system containing 100 g/L glucose and 5.5 g/L acetic acid, the lag phase of strain was 24 h shorter than that of control strain. Glucose consumption rate and ethanol titer of yPS002 got to 2.08 g/L/h and 44.25 g/L, respectively, which were 2.6- and 1.3-fold of the control strain. Transcriptional changes of INO1 gene and CTT1 gene confirmed that endogenous lycopene can decrease oxidative stress and improve intracellular environment. Biosynthesis of endogenous lycopene is first associated with enhancing tolerance to acetic acid in S. cerevisiae . We demonstrate that endogenous lycopene can decrease intracellular ROS level caused by acetic acid, thus increasing cell growth and ethanol production. This work innovatively   puts forward a new strategy for second generation bioethanol production during lignocellulosic fermentation.

Study of GaN nanorods converted from β-Ga2O3

NASA Astrophysics Data System (ADS)

Li, Yuewen; Xiong, Zening; Zhang, Dongdong; Xiu, Xiangqian; Liu, Duo; Wang, Shuang; Hua, Xuemei; Xie, Zili; Tao, Tao; Liu, Bin; Chen, Peng; Zhang, Rong; Zheng, Youdou

2018-05-01

We report here high-quality β-Ga2O3 nanorods (NRs) grown on sapphire substrates by hydrothermal method. Ammoniating the β-Ga2O3 NRs results in strain-free wurtzite gallium nitride (GaN) NRs. It was shown by XRD and Raman spectroscopy that β-Ga2O3 was partially converted to GaN/β-Ga2O3 at 1000 °C and then completely converted to GaN NRs at 1050 °C, as confirmed by high-resolution transmission electron microscopy (HRTEM). There is no band-edge emission of β-Ga2O3 in the cathodoluminescence spectrum, and only a deep-level broad emission observed at 3.68-3.73 eV. The band edge emission (3.39 eV) of GaN NRs converted from β-Ga2O3 can also be observed.

Deep-level traps in lightly Si-doped n-GaN on free-standing m-oriented GaN substrates

NASA Astrophysics Data System (ADS)

Yamada, H.; Chonan, H.; Takahashi, T.; Yamada, T.; Shimizu, M.

2018-04-01

In this study, we investigated the deep-level traps in Si-doped GaN epitaxial layers by metal-organic chemical vapor deposition on c-oriented and m-oriented free-standing GaN substrates. The c-oriented and m-oriented epitaxial layers, grown at a temperature of 1000 °C and V/III ratio of 1000, contained carbon atomic concentrations of 1.7×1016 and 4.0×1015 cm-3, respectively. A hole trap was observed at about 0.89 eV above the valence band maximum by minority carrier transient spectroscopy. The trap concentrations in the c-oriented and m-oriented GaN epitaxial layers were consistent with the carbon atomic concentrations from secondary ion mass spectroscopy and the yellow luminescence intensity at 2.21 eV from photoluminescence. The trap concentrations in the m-oriented GaN epitaxial layers were lower than those in the c-oriented GaN. Two electron traps, 0.24 and 0.61 eV below the conduction band (EC) minimum, were observed in the c-oriented GaN epitaxial layer. In contrast, the m-oriented GaN epitaxial layer was free from the electron trap at EC - 0.24 eV, and the trap concentration at EC - 0.61 eV in the m-oriented GaN epitaxial layer was lower than that in the c-oriented GaN epitaxial layer. The m-oriented GaN epitaxial layer exhibited fewer hole and electron traps compared to the c-oriented GaN epitaxial layers.

Are endogenous cardenolides controlled by atrial natriuretic peptide.

PubMed

Brar, Kanwarjeet S; Gao, Yonglin; El-Mallakh, Rif S

2016-07-01

Endogenous cardenolides are digoxin-like substances and ouabain-like substances that have been implicated in the pathogenesis of hypertension and mood disorders in clinical and pre-clinical studies. Regulatory signals for endogenous cardenolides are still unknown. These endogenous compounds are believed to be produced by the adrenal gland in the periphery and the hypothalamus in the central nervous system, and constitute part of an hormonal axis that may regulate the catalytic activity of the α subunit of Na(+)/K(+)-ATPase. A review of literature suggests that there is great overlap in physiological environments that are associated with either elevations or reductions in the levels of atrial natriuretic peptide (ANP) and endogenous cardenolides. This suggests that these two factors may share a common regulatory signal or perhaps that ANP may be involved in the regulation of endogenous cardenolides. Copyright © 2016. Published by Elsevier Ltd.

Effects of Glycyrrhetinic Acid on GSH Synthesis Induced by Realgar in the Mouse Hippocampus: Involvement of System [Formula: see text], System [Formula: see text], MRP-1, and Nrf2.

PubMed

Wang, Yan-Lei; Chen, Mo; Huo, Tao-Guang; Zhang, Ying-Hua; Fang, Ying; Feng, Cong; Wang, Shou-Yun; Jiang, Hong

2017-05-01

Realgar, a type of mineral drug-containing arsenic, exhibits neurotoxicity. Brain glutathione (GSH) is crucial to protect the nervous system and to resist arsenic toxicity. Therefore, the main aim of this study was to explore the neurotoxic mechanisms of realgar and the protective effects of glycyrrhetinic acid (GA) by observing the effects of GA on the hippocampal GSH biosynthetic pathway after exposure to realgar. Institute of Cancer Research (ICR) mice were randomly divided into five groups: a control group, a GA control group, a realgar alone group, a low-dose GA intervention group, and a high-dose GA intervention group. Cognitive ability was tested using an object recognition task (ORT). The ultrastructures of the hippocampal neurons and synapses were observed. mRNA and protein levels of EAAT1, EAAT2, EAAT3, xCT, Nrf2, HO-1, γ-GCS (GCLC, GCLM), and MRP-1 were measured, as was the cellular localization of EAAT3, xCT, MRP-1, and Nrf2. The levels of GSH in the hippocampus, the levels of glutamate (Glu) and cysteine (Cys) in the extracellular fluid of hippocampal CA1 region, and the levels of active sulfur in the brain were also investigated. The results indicate that realgar lowered hippocampal GSH levels, resulting in ultrastructural changes in hippocampal neurons and synapses and deficiencies in cognitive ability, ultimately inducing neurotoxicity. GA could trigger the expression of Nrf2, HO-1, EAAT1, EAAT2, EAAT3, xCT, MRP-1, GCLC, and GCLM. Additionally, the expression of γ-GT and the supply levels of Glu and Cys increased, ultimately causing a significant increase in hippocampal GSH to alleviate realgar-induced neurotoxicity. In conclusion, the findings from our study indicate that GA can antagonize decreased brain GSH levels induced by realgar and can lessen the neurotoxicity of realgar.

The -29G/A FSH receptor gene polymorphism is associated with higher FSH and LH levels in normozoospermic men.

PubMed

Tamburino, L; La Vignera, S; Tomaselli, V; Condorelli, R A; Cannarella, R; Mongioì, L M; Calogero, A E

2017-10-01

The functional role of the FSHR promoter -29G/A polymorphism (rs1394205) in men is not clear. Some studies failed to find a relationship between the FSHR -29G/A and follicle-stimulating hormone (FSH) levels and did not associate the SNP with male infertility. Only one study showed that the FSHR -29 SNP modulates serum FSH levels in Baltic young male cohort. Because the SNP -29G/A has to be shown to have a strong effect on in vitro transcription activity of the FSHR promoter and the activation of FSHR is necessary for a normal FSH function, this study was undertaken to assess whether the FSHR -29G/A SNP modulates the gonadal endocrine function in men. A total of 200 men with alteration of conventional sperm parameters or normozoospermia (according to the parameters WHO 2010), were genotyped by TaqMan Assay. Hormone levels were measured by immunoassay, and sperm analysis was performed according to the World Health Organization criteria. A significant gradient of increasing FSH levels across the FSHR -29G/A genotypes was observed (p < 0.01). Among normozoospermic men (n = 110), those with FSHR -29A-allele carriers (GA + AA and AA) had higher serum FSH (p < 0.01) and LH levels (p < 0.05) and higher body mass index (BMI) (p < 0.01) compared to men with the GG genotype. The carrier status of rs1394205 genotypes did not affect the other endocrine parameters neither in men with altered sperm parameters nor in normozoospermic men. The FSHR -29G/A polymorphism modulates FSH and, for the first time, LH serum levels and BMI in normozoospermic men. These findings underline the importance to pay close attention to the studies of genetic variations associated with clinical-endocrine parameters.

Guided bone regeneration produced by new mineralized and reticulated collagen membranes in critical-sized rat calvarial defects

PubMed Central

Leitão, Renata FC; Figueiró, Sônia D; Góes, Júlio C; Lima, Vilma; Silveira, Charles O; Brito, Gerly AC

2015-01-01

The aim of this study was to evaluate the bone regenerative effect of glutaraldehyde (GA) cross-linking on mineralized polyanionic collagen membranes in critical-sized defects on rat calvarias. Bone calvarial defects were induced in Wistar rats, which were then divided into five groups: a sham group; a control group, which received a commercial membrane; and GA, 25GA, and 75GA groups, which received one of three different polyanionic collagen membranes mineralized by 0, 25, or 75 hydroxyapatite cycles and then cross-linked by GA. Bone formation was evaluated based on digital radiography and computerized tomography. Histological analyses were performed 4 and 12 weeks after the surgical procedure to observe bone formation, membrane resorption, and fibrous tissue surrounding the membranes. Measurement of myeloperoxidase activity, tumor necrosis factor alpha, and interleukin 1beta production was performed 24 h after surgery. The percentage of new bone formation in the GA, 25GA, and 75GA groups was higher compared with the control and sham groups. In the GA and 25 GA groups, the membranes were still in place and were contained in a thick fibrous capsule after 12 weeks. No significant difference was found among the groups regarding myeloperoxidase activity and interleukin 1beta levels, although the GA, 25GA, and 75GA groups presented decreased levels of tumor necrosis factor alpha compared with the control group. These new GA cross-linked membranes accelerated bone healing of the calvarium defects and did not induce inflammation. In addition, unlike the control membrane, the experimental membranes were not absorbed during the analyzed period, so they may offer advantages in large bone defects where prolonged membrane barrier functions are desirable. PMID:25245073

Fermi level pinning at epitaxial Si on GaAs(100) interfaces

NASA Astrophysics Data System (ADS)

Silberman, J. A.; de Lyon, T. J.; Woodall, J. M.

1991-12-01

GaAs Schottky barrier contacts and metal-insulator-semiconductor structures that include thin epitaxial Si interfacial layers operate in a manner consistent with an unpinned Fermi level at the GaAs interface. These findings raise the question of whether this effect is an intrinsic property of the epitaxial GaAs(100)-Si interface. We have used x-ray photoemission spectroscopy to monitor the Fermi level position during in situ growth of thin epitaxial Si layers. In particular, films formed on heavily doped n- and p-type substrates were compared so as to use the large depletion layer fields available with high impurity concentration as a field-effect probe of the interface state density. The results demonstrate that epitaxial bonding at the interface alone is insufficient to eliminate Fermi level pinning, indicating that other mechanisms affect the interfacial charge balance in the devices that utilize Si interlayers.

EL2 deep-level transient study in semi-insulating GaAs using positron-lifetime spectroscopy

NASA Astrophysics Data System (ADS)

Shan, Y. Y.; Ling, C. C.; Deng, A. H.; Panda, B. K.; Beling, C. D.; Fung, S.

1997-03-01

Positron lifetime measurements performed on Au/GaAs samples at room temperature with an applied square-wave ac bias show a frequency dependent interface related lifetime intensity that peaks around 0.4 Hz. The observation is explained by the ionization of the deep-donor level EL2 to EL2+ in the GaAs region adjacent to the Au/GaAs interface, causing a transient electric field to be experienced by positrons drifting towards the interface. Without resorting to temperature scanning or any Arrhenius plot the EL2 donor level is found to be located 0.80+/-0.01+/-0.05 eV below the conduction-band minimum, where the first error estimate is statistical and the second systematic. The result suggests positron annihilation may, in some instances, act as an alternative to capacitance transient spectroscopies in characterizing deep levels in both semiconductors and semi-insulators.

Identification of the primary compensating defect level responsible for determining blocking voltage of vertical GaN power diodes

DOE PAGES

King, M. P.; Kaplar, R. J.; Dickerson, J. R.; ...

2016-10-31

Electrical performance and characterization of deep levels in vertical GaN P-i-N diodes grown on low threading dislocation density (~10 4 –10 6 cm –2) bulk GaN substrates are investigated. The lightly doped n drift region of these devices is observed to be highly compensated by several prominent deep levels detected using deep level optical spectroscopy at E c-2.13, 2.92, and 3.2 eV. A combination of steady-state photocapacitance and lighted capacitance-voltage profiling indicates the concentrations of these deep levels to be N t = 3 × 10 12, 2 × 10 15, and 5 × 10 14 cm –3, respectively. Themore » E c-2.92 eV level is observed to be the primary compensating defect in as-grown n-type metal-organic chemical vapor deposition GaN, indicating this level acts as a limiting factor for achieving controllably low doping. The device blocking voltage should increase if compensating defects reduce the free carrier concentration of the n drift region. Understanding the incorporation of as-grown and native defects in thick n-GaN is essential for enabling large V BD in the next-generation wide-bandgap power semiconductor devices. Furthermore, controlling the as-grown defects induced by epitaxial growth conditions is critical to achieve blocking voltage capability above 5 kV.« less

Addressing the need for biomarker liquid chromatography/mass spectrometry assays: a protocol for effective method development for the bioanalysis of endogenous compounds in cerebrospinal fluid.

PubMed

Benitex, Yulia; McNaney, Colleen A; Luchetti, David; Schaeffer, Eric; Olah, Timothy V; Morgan, Daniel G; Drexler, Dieter M

2013-08-30

Research on disorders of the central nervous system (CNS) has shown that an imbalance in the levels of specific endogenous neurotransmitters may underlie certain CNS diseases. These alterations in neurotransmitter levels may provide insight into pathophysiology, but can also serve as disease and pharmacodynamic biomarkers. To measure these potential biomarkers in vivo, the relevant sample matrix is cerebrospinal fluid (CSF), which is in equilibrium with the brain's interstitial fluid and circulates through the ventricular system of the brain and spinal cord. Accurate analysis of these potential biomarkers can be challenging due to low CSF sample volume, low analyte levels, and potential interferences from other endogenous compounds. A protocol has been established for effective method development of bioanalytical assays for endogenous compounds in CSF. Database searches and standard-addition experiments are employed to qualify sample preparation and specificity of the detection thus evaluating accuracy and precision. This protocol was applied to the study of the histaminergic neurotransmitter system and the analysis of histamine and its metabolite 1-methylhistamine in rat CSF. The protocol resulted in a specific and sensitive novel method utilizing pre-column derivatization ultra high performance liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS), which is also capable of separating an endogenous interfering compound, identified as taurine, from the analytes of interest. Copyright © 2013 John Wiley & Sons, Ltd.

A quantitative and qualitative review of the effects of testosterone on the function and structure of the human social-emotional brain.

PubMed

Heany, Sarah J; van Honk, Jack; Stein, Dan J; Brooks, Samantha J

2016-02-01

Social and affective research in humans is increasingly using functional and structural neuroimaging techniques to aid the understanding of how hormones, such as testosterone, modulate a wide range of psychological processes. We conducted a meta-analysis of functional magnetic resonance imaging (fMRI) studies of testosterone administration, and of fMRI studies that measured endogenous levels of the hormone, in relation to social and affective stimuli. Furthermore, we conducted a review of structural MRI i.e. voxel based morphometry (VBM) studies which considered brain volume in relation to testosterone levels in adults and in children. In the included testosterone administration fMRI studies, which consisted of female samples only, bilateral amygdala/parahippocampal regions as well as the right caudate were significantly activated by social-affective stimuli in the testosterone condition. In the studies considering endogenous levels of testosterone, stimuli-invoked activations relating to testosterone levels were noted in the bilateral amygdala/parahippocampal regions and the brainstem. When the endogenous testosterone studies were split by sex, the significant activation of the brain stem was seen in the female samples only. Significant stimuli-invoked deactivations relating to endogenous testosterone levels were also seen in the right and left amygdala/parahippocampal regions studies. The findings of the VBM studies were less consistent. In adults larger volumes in the limbic and temporal regions were associated with higher endogenous testosterone. In children, boys showed a positive correlation between testosterone and brain volume in many regions, including the amygdala, as well as global grey matter volume, while girls showed a neutral or negative association between testosterone levels and many brain volumes. In conclusion, amygdalar and parahippocampal regions appear to be key target regions for the acute actions of testosterone in response to social and affective stimuli, while neurodevelopmentally the volumes of a broader network of brain structures are associated with testosterone levels in a sexually dimorphic manner.

68Ga-PSMA PET/CT in Patients With Biochemical Recurrence of Prostate Cancer: A Prospective, 2-Center Study.

PubMed

Zacho, Helle D; Nielsen, Julie B; Dettmann, Katja; Haberkorn, Uwe; Langkilde, Niels C; Jensen, Jørgen B; Petersen, Lars J

2018-06-19

The aim of this study was to prospectively investigate the detection rate of Ga-PSMA PET/CT in biochemical recurrence (BCR) of prostate cancer and its impact on patient management. Patients with BCR after curatively intended treatment of prostate cancer were included. Each patient underwent a Ga-PSMA PET/CT. Changes in patient management based on the results of Ga-PSMA PET/CT were assessed. Seventy patients were included. Sixty-four patients (91%) had radical prostatectomy, of whom 17 patients (24%) received salvage radiation therapy due to first biochemical relapse. Six patients (9%) underwent radiation therapy as the primary treatment. Ga-PSMA PET/CT detected recurrent disease in 37 patients (53%). The detection rate was 22% for prostate-specific antigen (PSA) levels up to 0.5 ng/mL compared with 83% for PSA levels greater than 0.5 ng/mL. Pathological uptake of Ga-PSMA was observed in 4 (16%) of 21, 4 (44%) of 9, 0 of 1, 7 (70%) of 10, and 22 (88%) of 25 patients with PSA levels from 0.2 to 0.3 ng/mL, 0.31 to 0.4 ng/mL, 0.41 to 0.5 ng/mL, 0.51 to 1 ng/mL, and greater than 1 ng/mL, respectively. Prostate-specific antigen was significantly higher in PSMA-positive patients than in PSMA-negative patients. In 15 (22%) of 69 patients, the results caused a definite change in patient management, and in another 15 (22%) of 69 patients, Ga-PSMA PET/CT guided the choice of treatment. Ga-PSMA PET/CT detects lesions in a large proportion of patients with BCR. Detection rates at low PSA levels (<0.5 ng/mL) were notably below the values reported in previous retrospective studies; however, detection rates improved with increasing PSA levels.

Evaluation of GaAs low noise and power MMIC technologies to neutron, ionizing dose and dose rate effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Derewonko, H.; Bosella, A.; Pataut, G.

1996-06-01

An evaluation program of Thomson CSF-TCS GaAs low noise and power MMIC technologies to 1 MeV equivalent neutron fluence levels, up to 1 {times} 10{sup 15} n/cm{sup 2}, ionizing 1.17--1.33 MeV CO{sup 60} dose levels in excess of 200 Mrad(GaAs) and dose rate levels reaching 1.89 {times} 10{sup 11} rad(GaAs)/s is presented in terms of proper components and parameter choices, DC/RF electrical measurements and test methods under irradiation. Experimental results are explained together with drift analyses of electrical parameters that have determined threshold limits of component degradations. Modelling the effects of radiation on GaAs components relies on degradation analysis ofmore » active layer which appears to be the most sensitive factor. MMICs degradation under neutron fluence was simulated from irradiated FET data. Finally, based on sensitivity of technological parameters, rad-hard design including material, technology and MMIC design enhancement is discussed.« less

Doping of free-standing zinc-blende GaN layers grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Novikov, S. V.; Powell, R. E. L.; Staddon, C. R.; Kent, A. J.; Foxon, C. T.

2014-10-01

Currently there is high level of interest in developing of vertical device structures based on the group III nitrides. We have studied n- and p-doping of free-standing zinc-blende GaN grown by plasma-assisted molecular beam epitaxy (PA-MBE). Si was used as the n-dopant and Mg as the p-dopant for zinc-blende GaN. Controllable levels of doping with Si and Mg in free-standing zinc-blende GaN have been achieved by PA-MBE. The Si and Mg doping depth uniformity through the zinc-blende GaN layers have been confirmed by secondary ion mass spectrometry (SIMS). Controllable Si and Mg doping makes PA-MBE a promising method for the growth of conducting group III-nitrides bulk crystals.

Effects of Exogenous Salicylic Acid on Ganoderic Acid Biosynthesis and the Expression of Key Genes in the Ganoderic Acid Biosynthesis Pathway in the Lingzhi or Reishi Medicinal Mushroom, Ganoderma lucidum (Agaricomycetes).

PubMed

Cao, Peng-Fei; Wu, Chen-Gao; Dang, Zhi-Hao; Shi, Liang; Jiang, Ai-Liang; Ren, Ang; Zhao, Ming-Wen

2017-01-01

We demonstrate herein that salicylic acid (SA) can enhance ganoderic acid (GA) accumulation in the lingzhi or reishi medicinal mushroom Ganoderma lucidum. Following treatment with different concentrations of SA, the GA content was increased 22.72% to 43.04% compared with the control group. When the fungi were treated with 200 μmol/L SA at different times, the GA content was improved 10.21% to 35.24% compared with the control group. By choosing the optimum point based on response surface methodology, the GA content could be increased up to 229.03 μg/100 mg, which was improved 66.38% compared with the control group. When the fungi were treated with 200 μmol/L SA, the transcription levels of key genes in the GA biosynthesis pathway-squalene (SQ) synthase (sqs), lanosterol (Lano; osc), and hydroxy-3-methylglutaryl-coenzyme A reductase (hmgr)-were improved 119.6-, 3.2-, and 4.2-fold, respectively. In addition, following treatment with 100 μmol/L SA, the levels of Lano and SQ, which are intermediate metabolites of GA biosynthesis, were increased 2.8- and 1.4-fold, respectively. These results indicate that SA can regulate the expression of genes related to GA biosynthesis and increases the metabolic levels of Lano and SQ, thereby resulting in the accumulation of GA.

Gibberellin–Abscisic Acid Balances during Arbuscular Mycorrhiza Formation in Tomato

PubMed Central

Martín-Rodríguez, José A.; Huertas, Raúl; Ho-Plágaro, Tania; Ocampo, Juan A.; Turečková, Veronika; Tarkowská, Danuše; Ludwig-Müller, Jutta; García-Garrido, José M.

2016-01-01

Plant hormones have become appropriate candidates for driving functional plant mycorrhization programs, including the processes that regulate the formation of arbuscules in arbuscular mycorrhizal (AM) symbiosis. Here, we examine the role played by ABA/GA interactions regulating the formation of AM in tomato. We report differences in ABA and GA metabolism between control and mycorrhizal roots. Active synthesis and catabolism of ABA occur in AM roots. GAs level increases as a consequence of a symbiosis-induced mechanism that requires functional arbuscules which in turn is dependent on a functional ABA pathway. A negative interaction in their metabolism has been demonstrated. ABA attenuates GA-biosynthetic and increases GA-catabolic gene expression leading to a reduction in bioactive GAs. Vice versa, GA activated ABA catabolism mainly in mycorrhizal roots. The negative impact of GA3 on arbuscule abundance in wild-type plants is partially offset by treatment with ABA and the application of a GA biosynthesis inhibitor rescued the arbuscule abundance in the ABA-deficient sitiens mutant. These findings, coupled with the evidence that ABA application leads to reduce bioactive GA1, support the hypothesis that ABA could act modifying bioactive GA level to regulate AM. Taken together, our results suggest that these hormones perform essential functions and antagonize each other by oppositely regulating AM formation in tomato roots. PMID:27602046

A study of electrically active traps in AlGaN/GaN high electron mobility transistor

NASA Astrophysics Data System (ADS)

Yang, Jie; Cui, Sharon; Ma, T. P.; Hung, Ting-Hsiang; Nath, Digbijoy; Krishnamoorthy, Sriram; Rajan, Siddharth

2013-10-01

We have studied electron conduction mechanisms and the associated roles of the electrically active traps in the AlGaN layer of an AlGaN/GaN high electron mobility transistor structure. By fitting the temperature dependent I-V (Current-Voltage) curves to the Frenkel-Poole theory, we have identified two discrete trap energy levels. Multiple traces of I-V measurements and constant-current injection experiment all confirm that the main role of the traps in the AlGaN layer is to enhance the current flowing through the AlGaN barrier by trap-assisted electron conduction without causing electron trapping.

The influence of Mg doping on the formation of Ga vacancies and negative ions in GaN bulk crystals

NASA Astrophysics Data System (ADS)

Saarinen, K.; Nissilä, J.; Hautojärvi, P.; Likonen, J.; Suski, T.; Grzegory, I.; Lucznik, B.; Porowski, S.

1999-10-01

Gallium vacancies and negative ions are observed in GaN bulk crystals by applying positron lifetime spectroscopy. The concentration of Ga vacancies decreases with increasing Mg doping, as expected from the behavior of the VGa formation energy as a function of the Fermi level. The concentration of negative ions correlates with that of Mg impurities determined by secondary ion mass spectrometry. We thus attribute the negative ions to MgGa-. The negative charge of Mg suggests that Mg doping converts n-type GaN to semi-insulating mainly due to the electrical compensation of ON+ donors by MgGa- acceptors.

CYP714B1 and CYP714B2 encode gibberellin 13-oxidases that reduce gibberellin activity in rice.

PubMed

Magome, Hiroshi; Nomura, Takahito; Hanada, Atsushi; Takeda-Kamiya, Noriko; Ohnishi, Toshiyuki; Shinma, Yuko; Katsumata, Takumi; Kawaide, Hiroshi; Kamiya, Yuji; Yamaguchi, Shinjiro

2013-01-29

Bioactive gibberellins (GAs) control many aspects of growth and development in plants. GA(1) has been the most frequently found bioactive GA in various tissues of flowering plants, but the enzymes responsible for GA(1) biosynthesis have not been fully elucidated due to the enzymes catalyzing the 13-hydroxylation step not being identified. Because of the lack of mutants defective in this enzyme, biological significance of GA 13-hydroxylation has been unknown. Here, we report that two cytochrome P450 genes, CYP714B1 and CYP714B2, encode GA 13-oxidase in rice. Transgenic Arabidopsis plants that overexpress CYP714B1 or CYP714B2 show semidwarfism. There was a trend that the levels of 13-OH GAs including GA(1) were increased in these transgenic plants. Functional analysis using yeast or insect cells shows that recombinant CYP714B1 and CYP714B2 proteins can convert GA(12) into GA(53) (13-OH GA(12)) in vitro. Moreover, the levels of 13-OH GAs including GA(1) were decreased, whereas those of 13-H GAs including GA(4) (which is more active than GA(1)) were increased, in the rice cyp714b1 cyp714b2 double mutant. These results indicate that CYP714B1 and CYP714B2 play a predominant role in GA 13-hydroxylation in rice. The double mutant plants appear phenotypically normal until heading, but show elongated uppermost internode at the heading stage. Moreover, CYP714B1 and CYP714B2 expression was up-regulated by exogenous application of bioactive GAs. Our results suggest that GA 13-oxidases play a role in fine-tuning plant growth by decreasing GA bioactivity in rice and that they also participate in GA homeostasis.

Asymmetric gibberellin signaling regulates vacuolar trafficking of PIN auxin transporters during root gravitropism.

PubMed

Löfke, Christian; Zwiewka, Marta; Heilmann, Ingo; Van Montagu, Marc C E; Teichmann, Thomas; Friml, Jirí

2013-02-26

Gravitropic bending of plant organs is mediated by an asymmetric signaling of the plant hormone auxin between the upper and lower side of the respective organ. Here, we show that also another plant hormone, gibberellic acid (GA), shows asymmetric action during gravitropic responses. Immunodetection using an antibody against GA and monitoring GA signaling output by downstream degradation of DELLA proteins revealed an asymmetric GA distribution and response with the maximum at the lower side of gravistimulated roots. Genetic or pharmacological manipulation of GA levels or response affects gravity-mediated auxin redistribution and root bending response. The higher GA levels at the lower side of the root correlate with increased amounts of PIN-FORMED2 (PIN2) auxin transporter at the plasma membrane. The observed increase in PIN2 stability is caused by a specific GA effect on trafficking of PIN proteins to lytic vacuoles that presumably occurs downstream of brefeldin A-sensitive endosomes. Our results suggest that asymmetric auxin distribution instructive for gravity-induced differential growth is consolidated by the asymmetric action of GA that stabilizes the PIN-dependent auxin stream along the lower side of gravistimulated roots.

Ascorbic acid and reactive oxygen species are involved in the inhibition of seed germination by abscisic acid in rice seeds

PubMed Central

Ye, Nenghui; Zhu, Guohui; Liu, Yinggao; Liu, Rui; Shi, Lu; Jia, Liguo; Zhang, Jianhua

2012-01-01

The antagonism between abscisic acid (ABA) and gibberellin (GA) plays a key role in controlling seed germination, but the mechanism of antagonism during this process is not known. The possible links among ABA, reactive oxygen species (ROS), ascorbic acid (ASC), and GA during rice seed germination were investigated. Unlike in non-seed tissues where ROS production is increased by ABA, ABA reduced ROS production in imbibed rice seeds, especially in the embryo region. Such reduced ROS also led to an inhibition of ASC production. GA accumulation was also suppressed by a reduced ROS and ASC level, which was indicated by the inhibited expression of GA biosynthesis genes, amylase genes, and enzyme activity. Application of exogenous ASC can partially rescue seed germination from ABA treatment. Production of ASC, which acts as a substrate in GA biosynthesis, was significantly inhibited by lycorine which thus suppressed the accumulation of GA. Consequently, expression of GA biosynthesis genes was suppressed by the low levels of ROS and ASC in ABA-treated seeds. It can be concluded that ABA regulates seed germination in multiple dimensions. ROS and ASC are involved in its inhibition of GA biosynthesis. PMID:22200664

[Disposal of radioactive contaminated waste from Ga-68-PET - calculation of a clearance level for Ge-68].

PubMed

Solle, Alexander; Wanke, Carsten; Geworski, Lilli

2017-03-01

Ga-68-labeled radiotracers, particularly used for the detection of neuroendocrine tumors by means of Ga-68-DOTA-TATE or -DOTA-TOC or for the diagnosis of prostate cancer by means of Ga-68-labeled antigens (Ga 68-PSMA), become increasingly important. In addition to the high sensitivity and specificity of these radiopharmaceuticals, the short-lived radionuclide Ga-68 offers almost ideal nuclear characteristics for use in PET. Ga-68 is obtained from a germanium-gallium-generator system, so that the availability of Ga-68-labeled radiotracers is independent of an on-site-cyclotron regardless of the short half-life of Ga-68 of about 68minutes. Regarding the disposal of the radioactively contaminated waste from the preparation of the radiopharmaceutical, the eluted Ga-68 has to be considered to be additionally contaminated with its parent nuclide Ge-68. Due to this production-related impurity in combination with the short half-life of Ga-68, the radioactive waste has to be considered to be contaminated with Ge-68 and Ga-68 in radioactive equilibrium (hereafter referred to as Ge-68+). As there are no clearance levels for Ge-68+ given in the German Radiation Protection Ordinance, this work presents a method to calculate the missing value basing on a recommendation of the German Radiation Protection Commission in combination with simple geometric models of practical radiation protection. Regarding the relevant exposure scenarios, a limit value for the unrestricted clearance of Ge-68+ of 0.4 Bq/g was determined. Copyright © 2016. Published by Elsevier GmbH.

Electronic properties of core-shell nanowire resonant tunneling diodes

PubMed Central

2014-01-01

The electronic sub-band structure of InAs/InP/InAs/InP/InAs core-shell nanowire resonant tunneling diodes has been investigated in the effective mass approximation by varying the core radius and the thickness of the InP barriers and InAs shells. A top-hat, double-barrier potential profile and optimal energy configuration are obtained for core radii and surface shells >10 nm, InAs middle shells <10 nm, and 5 nm InP barriers. In this case, two sub-bands exist above the Fermi level in the InAs middle shell which belongs to the m = 0 and m = 1 ladder of states that have similar wave functions and energies. On the other hand, the lowest m = 0 sub-band in the core falls below the Fermi level but the m = 1 states do not contribute to the current transport since they reside energetically well above the Fermi level. We compare the case of GaAs/AlGaAs/GaAs/AlGaAs/GaAs which may conduct current with smaller applied voltages due to the larger effective mass of electrons in GaAs and discuss the need for doping. PMID:25288912

Electronic properties of core-shell nanowire resonant tunneling diodes.

PubMed

Zervos, Matthew

2014-01-01

The electronic sub-band structure of InAs/InP/InAs/InP/InAs core-shell nanowire resonant tunneling diodes has been investigated in the effective mass approximation by varying the core radius and the thickness of the InP barriers and InAs shells. A top-hat, double-barrier potential profile and optimal energy configuration are obtained for core radii and surface shells >10 nm, InAs middle shells <10 nm, and 5 nm InP barriers. In this case, two sub-bands exist above the Fermi level in the InAs middle shell which belongs to the m = 0 and m = 1 ladder of states that have similar wave functions and energies. On the other hand, the lowest m = 0 sub-band in the core falls below the Fermi level but the m = 1 states do not contribute to the current transport since they reside energetically well above the Fermi level. We compare the case of GaAs/AlGaAs/GaAs/AlGaAs/GaAs which may conduct current with smaller applied voltages due to the larger effective mass of electrons in GaAs and discuss the need for doping.

High kappa Dielectrics on InGaAs and GaN: Growth, Interfacial Structural Studies, and Surface Fermi Level Unpinning

DTIC Science & Technology

2010-12-24

nano-thick Al2O3, HfO2, and Ga2O3 (Gd2O3)/ InGaAs (and GaN) using high-resolution x-ray reflectivity using in-situ/ex-situ high-resolution synchrotron...aligned inversion-channel In0.75Ga0.25As MOSFETs using MBE- grown Al2O3/ Ga2O3 (Gd2O3) Chips integrating high κ’s/InGaAs and /Ge onto Si substrates have...using molecular beam epitaxy (MBE)-Al2O3/ Ga2O3 (Gd2O3) [GGO] and atomic layer deposited (ALD)-Al2O3, with gate lengths (LG) of 1 μm and 0.4 μm

High kappa Dielectrics on InGaAs and GaN - Growth, Interfacial Structural Studies, and Surface Fermi Level Unpinning

DTIC Science & Technology

2011-04-20

ALD-Al2O3 and in-situ MBE-Al2O3/ Ga2O3 (Gd2O3) [GGO] as the gate dielectrics. The advances of the InGaAs MOSFETs achieved will enable future CMOS...and GaN MOSFETs:  High-performance self-aligned inversion-channel In0.53Ga0.47As and In0.75Ga0.25As MOSFET’s with Al2O3/ Ga2O3 (Gd2O3) as gate... Ga2O3 (Gd2O3) as gate dielectrics Key accomplishments in devices of 1m gate length: High drain current of 1.23 mA/m High transcoductance of 714

Clinical study of the hypothesis of endogenous collateral wind on acute coronary syndrome: a review.

PubMed

Wang, Xian; Zhang, Cong; Yang, Ran; Zhu, Haiyan; Zhao, Huaibing; Li, Xiaoming

2014-01-01

Acute Coronary Syndrome (ACS), is a serious threat to people's health, and life, and in recent years, the incidence has increased yearly. This study was to propose the hypothesis of "endogenous collateral wind" based on the patho-mechanism of thrombogenesis complicated by ruptured plaque on ACS, and the theory of traditional Chinese medicine. Through successful coronary angiography (CAG), and intravascular ultrasound (IVUS), patients with coronary artery disease were made the differential diagnosis such as blood stasis, blood stasis due to phlegm obstruction, and endogenous collateral wind. The levels of plasma inflammatory marker were measured to study on the characteristics of "endogenous collateral wind". Luo heng dripping pills with promoting blood circulation to expel wind-evil, and remove wetness were made based on the hypothesis of "endogenous collateral wind" on ACS. Patients with unstable angina were randomly divided into 3, groups based on therapeutic methods: conventional therapy group, Luo Heng dripping pills group and Tongxinluo caps. Differences among groups were compared. There were great changes in number and degree of coronary arteriostenosis confirmed by CAG, the types of ACC/AHA lesion and Levin lesion confirmed by CAG, remodeling index, positive or negative remodeling percentage measured by IVUS, the plasma levels of plasma inflammatory marker measured by ELLSA in the patients with endogenous collateral wind, compared with patients with blood stasis and blood stasis due to phlegm obstruction. The total effective rate of improved angina in Luo Heng dripping pills group was significantly higher than those in other two groups. The levels of plasma inflammatory marker were significantly lower in Luo Heng dripping pills group. There were some pathological basis which were found about the hypothesis of "endogenous collateral wind" on acute coronary syndrome. It provided evidences for patients with coronary artery disease treated by medicines with expelling evil-wind, and removing wetness.

Detection of endogenous boldenone in the entire male horses.

PubMed

Ho, Emmie N M; Yiu, Kenneth C H; Tang, Francis P W; Dehennin, Louis; Plou, Philippe; Bonnaire, Yves; Wan, Terence S M

2004-09-05

Boldenone (1,2-dehydrotestosterone) is a common veterinary anabolic agent. Its structure is very similar to testosterone. Testosterone is endogenous in the horse, whereas there has been no report concerning the detection of endogenous boldenone. This paper reports the direct observation of sulphate conjugate of boldenone in equine urine from entires. The detection procedures involved solid-phase extraction, immunoaffinity column (IAC) purification, and then LC-MS-MS analysis on a Q-ToF instrument. The identification of boldenone sulphate has provided direct evidence for the endogenous nature of boldenone in entire male horses. Quantification data for the normal level of boldenone in Hong Kong racehorses will also be discussed.

Role of surface energy on the morphology and optical properties of GaP micro & nano structures grown on polar and non-polar substrates

NASA Astrophysics Data System (ADS)

Roychowdhury, R.; Kumar, Shailendra; Wadikar, A.; Mukherjee, C.; Rajiv, K.; Sharma, T. K.; Dixit, V. K.

2017-10-01

Role of surface energy on the morphology, crystalline quality, electronic structure and optical properties of GaP layer grown on Si (001), Si (111), Ge (111) and GaAs (001) is investigated. GaP layers are grown on four different substrates under identical growth kinetics by metal organic vapour phase epitaxy. The atomic force microscopy images show that GaP layer completely covers the surface of GaAs substrate. On the other hand, the surfaces of Si (001), Si (111), Ge (111) substrates are partially covered with crystallographically morphed GaP island type micro and nano-structures. Origin of these crystallographically morphed GaP island is explained by the theoretical calculation of surface energy of the layer and corresponding substrates respectively. The nature of GaP island type micro and nano-structures and layers are single crystalline with existence of rotational twins on Si and Ge (111) substrates which is confirmed by the phi, omega and omega/2theta scans of high resolution x-ray diffraction. The electronic valence band offsets between the GaP and substrates have been determined from the valence band spectra of ultraviolet photoelectron spectroscopy. The valence electron plasmon of GaP are investigated by studying the energy values of Ga (3d) core level along with loss peaks in the energy dependent photoelectron spectra. The peak observed within the range of 3-6 eV from the Ga (3d) core level in the photoelectron spectra are associated to inter band transitions as their energy values are estimated from the pseudo dielectric function by the spectroscopic ellipsometry.

Endogenous enzyme activities and polyamine levels in diverse rice cultivars depend on the genetic background and are not affected by the presence of the hygromycin phosphotransferase selectable marker.

PubMed

Lepri, O.; Bassie, L.; Thu-Hang, P.; Christou, P.; Capell, T.

2002-09-01

We used the polyamine biosynthetic pathway and rice as a relevant model to understand the genetic basis of variation in endogenous levels of metabolites and key enzymes involved in the pathway. Wild-type tissues and also tissues containing a commonly used selectable marker gene were employed. We detected a wide variation in levels of arginine decarboxylase activity and in the three polyamines, putrescine, spermidine and spermine, in different tissues and varieties, but this was not dependent on the presence of the selectable marker. A more-extensive profile of enzyme activities (ADC, ODC, SAMDC, DAO and PAO) and polyamine levels in different tissues was generated in two different varieties. Our results indicate that genetic background is important in terms of the basal levels of metabolites and enzyme activity, particularly in situations in which we aim to engineer metabolic pathways that are also encoded by homologous endogenous genes. We did not find any evidence that the presence of a selectable marker in any way influences enzyme activity or metabolite levels.

Thermodynamics of GaN(s)-NH3(v)+N2(v)+H2(v) system - Electronic aspects of the processes at GaN(0001) surface

NASA Astrophysics Data System (ADS)

Kempisty, Pawel; Strak, Pawel; Sakowski, Konrad; Krukowski, Stanislaw

2017-08-01

Comprehensive analysis of GaN(0001) surface in equilibrium with ammonia/hydrogen mixture was undertaken using results of ab initio calculations. Adsorption energies of the species derived from ammonia and molecular hydrogen and their stable sites were obtained. It was shown that the adsorption process type and energy depend on the position of Fermi level at the surface. Hydrogen decomposes into two separate H atoms, always adsorbed in the positions on top of the surface Ga atoms (On-top). Ammonia adsorption at GaN(0001) surface proceeds molecularly to ammonia in the On-top position or dissociatively into NH2 radicals in bridge (NH2-bridge) or On-top positions or into NH radicals in H3 (NH-H3) site. Presence of these species affects Fermi level pinning at the surface due to creation of new surface states. The Fermi level pinning in function of the surface attached species concentration was determined using extended electron counting rule (EECR). Results of ab initio calculations fully proved validity of the EECR predictions. Thermodynamic analysis of the surface in equilibrium with molecular hydrogen and ammonia vapor mixture is made giving the range of ammonia and hydrogen pressures, corresponding to Fermi level pinned at Ga-broken bond state for NH-H3&H and NH3&H and NH2-bridge&H coverage and at VBM for NH3 & H coverage. As the region of Fermi level pinned at Ga broken bond state corresponds to very low pressures, at pressures close to normal, GaN(0001) surface is almost totally covered by H, NH3 and NH2 located in On-top positions. It is also shown however that dominant portion of the hydrogen and ammonia pressures corresponds to Fermi level not pinned. Among them are these corresponding to MOVPE and HVPE growth conditions in which the surface is almost fully covered by NH3, NH2 and H species in On-top positions.

Endogeous sulfur dioxide protects against oleic acid-induced acute lung injury in association with inhibition of oxidative stress in rats.

PubMed

Chen, Siyao; Zheng, Saijun; Liu, Zhiwei; Tang, Chaoshu; Zhao, Bin; Du, Junbao; Jin, Hongfang

2015-02-01

The role of endogenous sulfur dioxide (SO2), an efficient gasotransmitter maintaining homeostasis, in the development of acute lung injury (ALI) remains unidentified. We aimed to investigate the role of endogenous SO2 in the pathogenesis of ALI. An oleic acid (OA)-induced ALI rat model was established. Endogenous SO2 levels, lung injury, oxidative stress markers and apoptosis were examined. OA-induced ALI rats showed a markedly downregulated endogenous SO2/aspartate aminotransferase 1 (AAT1)/AAT2 pathway and severe lung injury. Chemical colorimetry assays demonstrated upregulated reactive oxygen species generation and downregulated antioxidant capacity in OA-induced ALI rats. However, SO2 increased endogenous SO2 levels, protected against oxidative stress and alleviated ALI. Moreover, compared with OA-treated cells, in human alveolar epithelial cells SO2 downregulated O2(-) and OH(-) generation. In contrast, L-aspartic acid-β-hydroxamate (HDX, Sigma-Aldrich Corporation), an inhibitor of endogenous SO2 generating enzyme, promoted free radical generation, upregulated poly (ADP-ribose) polymerase expression, activated caspase-3, as well as promoted cell apoptosis. Importantly, apoptosis could be inhibited by the free radical scavengers glutathione (GSH) and N-acetyl-L-cysteine (NAC). The results suggest that SO2/AAT1/AAT2 pathway might protect against the development of OA-induced ALI by inhibiting oxidative stress.

lin-4 and the NRDE pathway are required to activate a transgenic lin-4 reporter but not the endogenous lin-4 locus in C. elegans.

PubMed

Jiao, Alan L; Foster, Daniel J; Dixon, Julia; Slack, Frank J

2018-01-01

As the founding member of the microRNA (miRNA) gene family, insights into lin-4 regulation and function have laid a conceptual foundation for countless miRNA-related studies that followed. We previously showed that a transcriptional lin-4 reporter in C. elegans was positively regulated by a lin-4-complementary element (LCE), and by lin-4 itself. In this study, we sought to (1) identify additional factors required for lin-4 reporter expression, and (2) validate the endogenous relevance of a potential positive autoregulatory mechanism of lin-4 expression. We report that all four core nuclear RNAi factors (nrde-1, nrde-2, nrde-3 and nrde-4), positively regulate lin-4 reporter expression. In contrast, endogenous lin-4 levels were largely unaffected in nrde-2;nrde-3 mutants. Further, an endogenous LCE deletion generated by CRISPR-Cas9 revealed that the LCE was also not necessary for the activity of the endogenous lin-4 promoter. Finally, mutations in mature lin-4 did not reduce primary lin-4 transcript levels. Taken together, these data indicate that under growth conditions that reveal effects at the transgenic locus, a direct, positive autoregulatory mechanism of lin-4 expression does not occur in the context of the endogenous lin-4 locus.

Regulation of Intracellular Copper by Induction of Endogenous Metallothioneins Improves the Disease Course in a Mouse Model of Amyotrophic Lateral Sclerosis.

PubMed

Tokuda, Eiichi; Watanabe, Shunsuke; Okawa, Eriko; Ono, Shin-ichi

2015-04-01

Mutations in SOD1 cause amyotrophic lateral sclerosis (ALS), an incurable motor neuron disease. The pathogenesis of the disease is poorly understood, but intracellular copper dyshomeostasis has been implicated as a key process in the disease. We recently observed that metallothioneins (MTs) are an excellent target for the modification of copper dyshomeostasis in a mouse model of ALS (SOD1(G93A)). Here, we offer a therapeutic strategy designed to increase the level of endogenous MTs. The upregulation of endogenous MTs by dexamethasone, a synthetic glucocorticoid, significantly improved the disease course and rescued motor neurons in SOD1(G93A) mice, even if the induction was initiated when peak body weight had decreased by 10%. Neuroprotection was associated with the normalization of copper dyshomeostasis, as well as with decreased levels of SOD1(G93A) aggregates. Importantly, these benefits were clearly mediated in a MT-dependent manner, as dexamethasone did not provide any protection when endogenous MTs were abolished from SOD1(G93A) mice. In conclusion, the upregulation of endogenous MTs represents a promising strategy for the treatment of ALS linked to mutant SOD1.

The Increased Endogenous Sulfur Dioxide Acts as a Compensatory Mechanism for the Downregulated Endogenous Hydrogen Sulfide Pathway in the Endothelial Cell Inflammation

PubMed Central

Zhang, Da; Wang, Xiuli; Tian, Xiaoyu; Zhang, Lulu; Yang, Guosheng; Tao, Yinghong; Liang, Chen; Li, Kun; Yu, Xiaoqi; Tang, Xinjing; Tang, Chaoshu; Zhou, Jing; Kong, Wei; Du, Junbao; Huang, Yaqian; Jin, Hongfang

2018-01-01

Endogenous hydrogen sulfide (H2S) and sulfur dioxide (SO2) are regarded as important regulators to control endothelial cell function and protect endothelial cell against various injuries. In our present study, we aimed to investigate the effect of endogenous H2S on the SO2 generation in the endothelial cells and explore its significance in the endothelial inflammation in vitro and in vivo. The human umbilical vein endothelial cell (HUVEC) line (EA.hy926), primary HUVECs, primary rat pulmonary artery endothelial cells (RPAECs), and purified aspartate aminotransferase (AAT) protein from pig heart were used for in vitro experiments. A rat model of monocrotaline (MCT)-induced pulmonary vascular inflammation was used for in vivo experiments. We found that endogenous H2S deficiency caused by cystathionine-γ-lyase (CSE) knockdown increased endogenous SO2 level in endothelial cells and enhanced the enzymatic activity of AAT, a major SO2 synthesis enzyme, without affecting the expressions of AAT1 and AAT2. While H2S donor could reverse the CSE knockdown-induced increase in the endogenous SO2 level and AAT activity. Moreover, H2S donor directly inhibited the activity of purified AAT protein, which was reversed by a thiol reductant DTT. Mechanistically, H2S donor sulfhydrated the purified AAT1/2 protein and rescued the decrease in the sulfhydration of AAT1/2 protein in the CSE knockdown endothelial cells. Furthermore, an AAT inhibitor l-aspartate-β-hydroxamate (HDX), which blocked the upregulation of endogenous SO2/AAT generation induced by CSE knockdown, aggravated CSE knockdown-activated nuclear factor-κB pathway in the endothelial cells and its downstream inflammatory factors including ICAM-1, TNF-α, and IL-6. In in vivo experiment, H2S donor restored the deficiency of endogenous H2S production induced by MCT, and reversed the upregulation of endogenous SO2/AAT pathway via sulfhydrating AAT1 and AAT2. In accordance with the results of the in vitro experiment, HDX exacerbated the pulmonary vascular inflammation induced by the broken endogenous H2S production in MCT-treated rat. In conclusion, for the first time, the present study showed that H2S inhibited endogenous SO2 generation by inactivating AAT via the sulfhydration of AAT1/2; and the increased endogenous SO2 generation might play a compensatory role when H2S/CSE pathway was downregulated, thereby exerting protective effects in endothelial inflammatory responses in vitro and in vivo. PMID:29760703

Comparative transcriptome analysis reveals distinct ethylene-independent regulation of ripening in response to low temperature in kiwifruit.

PubMed

Asiche, William O; Mitalo, Oscar W; Kasahara, Yuka; Tosa, Yasuaki; Mworia, Eric G; Owino, Willis O; Ushijima, Koichiro; Nakano, Ryohei; Yano, Kentaro; Kubo, Yasutaka

2018-03-21

Kiwifruit are classified as climacteric since exogenous ethylene (or its analogue propylene) induces rapid ripening accompanied by ethylene production under positive feedback regulation. However, most of the ripening-associated changes (Phase 1 ripening) in kiwifruit during storage and on-vine occur largely in the absence of any detectable ethylene. This ripening behavior is often attributed to basal levels of system I ethylene, although it is suggested to be modulated by low temperature. To elucidate the mechanisms regulating Phase 1 ripening in kiwifruit, a comparative transcriptome analysis using fruit continuously exposed to propylene (at 20 °C), and during storage at 5 °C and 20 °C was conducted. Propylene exposure induced kiwifruit softening, reduction of titratable acidity (TA), increase in soluble solids content (SSC) and ethylene production within 5 days. During storage, softening and reduction of TA occurred faster in fruit at 5 °C compared to 20 °C although no endogenous ethylene production was detected. Transcriptome analysis revealed 3761 ripening-related differentially expressed genes (DEGs), of which 2742 were up-regulated by propylene while 1058 were up-regulated by low temperature. Propylene exclusively up-regulated 2112 DEGs including those associated with ethylene biosynthesis and ripening such as AcACS1, AcACO2, AcPL1, AcXET1, Acβ-GAL, AcAAT, AcERF6 and AcNAC7. Similarly, low temperature exclusively up-regulated 467 DEGS including AcACO3, AcPL2, AcPMEi, AcADH, Acβ-AMY2, AcGA2ox2, AcNAC5 and AcbZIP2 among others. A considerable number of DEGs such as AcPG, AcEXP1, AcXET2, Acβ-AMY1, AcGA2ox1, AcNAC6, AcMADS1 and AcbZIP1 were up-regulated by either propylene or low temperature. Frequent 1-MCP treatments failed to inhibit the accelerated ripening and up-regulation of associated DEGs by low temperature indicating that the changes were independent of ethylene. On-vine kiwifruit ripening proceeded in the absence of any detectable endogenous ethylene production, and coincided with increased expression of low temperature-responsive DEGs as well as the decrease in environmental temperature. These results indicate that kiwifruit possess both ethylene-dependent and low temperature-modulated ripening mechanisms that are distinct and independent of each other. The current work provides a foundation for elaborating the control of these two ripening mechanisms in kiwifruit.

High-Level Operations in Nonprocedural Programming Languages.

DTIC Science & Technology

1983-12-01

defining type specific operators. Abstract data type has been applied to the nonprocedural language NOPAL [Sang8O]. It was primarily used as a tool...level operation is transformed using the integral operation MATINV as follows: 1 GA IS GROUP, 2 GRA(*) IS GROUP, 3 AUX(*) IS FIELD (DEC FLOAT); I GI...IS GROUP, 2 GRI(*) IS GROUP, 3 INV(*) IS FIELD (DEC FLOAT); AUX = A; GI = MATINV( GA ); C = INV; In code generation, the assertion GI=MATINV( GA ) is

Defect-Reduction Mechanism for Improving Radiative Efficiency in InGaN/GaN Light-Emitting Diodes using InGaN Underlayers

DOE PAGES

Armstrong, Andrew M.; Bryant, Benjamin N.; Crawford, Mary H.; ...

2015-04-01

The influence of a dilute In xGa 1-xN (x~0.03) underlayer (UL) grown below a single In 0.16Ga 0.84N quantum well (SQW), within a light-emitting diode(LED), on the radiative efficiency and deep level defect properties was studied using differential carrier lifetime (DCL) measurements and deep level optical spectroscopy (DLOS). DCL measurements found that inclusion of the UL significantly improved LED radiative efficiency. At low current densities, the non-radiative recombination rate of the LED with an UL was found to be 3.9 times lower than theLED without an UL, while the radiative recombination rates were nearly identical. This, then, suggests that themore » improved radiative efficiency resulted from reduced non-radiative defect concentration within the SQW. DLOS measurement found the same type of defects in the InGaN SQWs with and without ULs. However, lighted capacitance-voltage measurements of the LEDs revealed a 3.4 times reduction in a SQW-related near-mid-gap defect state for the LED with an UL. Furthermore, quantitative agreement in the reduction of both the non-radiative recombination rate (3.9×) and deep level density (3.4×) upon insertion of an UL corroborates deep level defect reduction as the mechanism for improved LED efficiency.« less

Donors, Acceptors, and Traps in AlGaN and AlGaN/GaN Epitaxial Layers

DTIC Science & Technology

2006-07-31

the background. 3.3 Positron annihilation spectroscopy (PAS): acceptor-type defects Positrons injected into defect-free GaN are annihilated by electrons...electron concentration n, and the average Ga-vacancy VGa concentration deduced from positron annihilation spectroscopy . 0.09 3.47 3.46 - 3.45 •ŗ.47225...of this paper, are often investigated by deep level transient spectroscopy (DLTS), and the usual analysis of DLTS data is based on the assumption that

GENETIC MODIFICATION OF GIBBERELLIC ACID SIGNALING TO PROMOTE CARBON SEQUESTRATION IN TREE ROOTS AND STEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Busov, Victor

Semidwarfism has been used extensively in row crops and horticulture to promote yield, reduce lodging, and improve harvest index, and it might have similar benefits for trees for short-rotation forestry or energy plantations, reclamation, phytoremediation, or other applications. We studied the effects of the dominant semidwarfism transgenes GA Insensitive (GAI) and Repressor of GAI-Like, which affect gibberellin (GA) action, and the GA catabolic gene, GA 2-oxidase, in nursery beds and in 2-year-old high-density stands of hybrid poplar (Populus tremula - Populus alba). Twenty-nine traits were analyzed, including measures of growth, morphology, and physiology. Endogenous GA levels were modified in mostmore » transgenic events; GA(20) and GA(8), in particular, had strong inverse associations with tree height. Nearly all measured traits varied significantly among genotypes, and several traits interacted with planting density, including aboveground biomass, root-shoot ratio, root fraction, branch angle, and crown depth. Semidwarfism promoted biomass allocation to roots over shoots and substantially increased rooting efficiency with most genes tested. The increased root proportion and increased leaf chlorophyll levels were associated with changes in leaf carbon isotope discrimination, indicating altered water use efficiency. Semidwarf trees had dramatically reduced growth when in direct competition with wild-type trees, supporting the hypothesis that semidwarfism genes could be effective tools to mitigate the spread of exotic, hybrid, and transgenic plants in wild and feral populations. We modified gibberellin (GA) metabolism and signaling in transgenic poplars using dominant transgenes and studied their effects for 3 years under field conditions. The transgenes that we employed either reduced the bioactive GAs, or attenuated their signaling. The majority of transgenic trees had significant and in many cases dramatic changes in height, crown architecture, foliage morphology, flowering onset, floral structure, and vegetative phenology. Most transgenes elicited various levels of height reduction consistent with the roles of GA in elongation growth. Several other growth traits were proportionally reduced, including branch length, internode distance, and leaf length. In contrast to elongation growth, stem diameter growth was much less affected, suggesting that semi-dwarf trees in dense stands might provide high levels of biomass production and carbon sequestration. The severity of phenotypic effects was strongly correlated with transgene expression among independent transgenic events, but often in a non-linear manner, the form of which varied widely among constructs. The majority of semi-dwarfed, transgenic plants showed delayed bud flush and early bud set, and expression of a native GAI transgene accelerated first time flowering in the field. All of the phenotypic changes observed in multiple years were stable over the 3 years of field study. Our results suggest that transgenic modification of GA action may be useful for producing semi-dwarf trees with modified growth and morphology for horticulture and other uses. We studied the poplar C(19) gibberellin 2-oxidase (GA2ox) gene subfamily. We show that a set of paralogous gene pairs differentially regulate shoot and root development. ? PtGA2ox4 and its paralogous gene PtGA2ox5 are primarily expressed in aerial organs, and overexpression of PtGA2ox5 produced a strong dwarfing phenotype characteristic of GA deficiency. Suppression of PtGA2ox4 and PtGA2ox5 led to increased biomass growth, but had no effect on root development. By contrast, the PtGA2ox2 and PtGA2ox7 paralogous pair was predominantly expressed in roots, and when these two genes were RNAi-suppressed it led to a decrease of root biomass. ? The morphological changes in the transgenic plants were underpinned by tissue-specific increases in bioactive GAs that corresponded to the predominant native expression of the targeted paralogous gene pair. Although RNAi suppression of both paralogous pairs led to changes in wood development, they were much greater in the transgenics with suppressed PtGA2ox4 and PtGA2ox5. The degree of gene suppression in independent events was strongly associated with phenotypes, demonstrating dose-dependent control of growth by GA2ox RNA concentrations. ? The expression and transgenic modifications reported here show that shoot- and leaf-expressed PtGA2ox4 and PtGA2ox5 specifically restrain aerial shoot growth, while root-expressed PtGA2ox2 and PtGA2ox7 promote root development. Genes controlling plant growth and form are of considerable interest, because they affect survival and productivity traits, and are largely unknown or poorly characterized. The SHORT INTERNODES(SHI) gene is one of a 10-member SHI-RELATED SEQUENCE (SRS) gene family in Arabidopsis that includes important developmental regulators. ? Using comparative sequence analysis of the SRS gene families in poplar and Arabidopsis, we identified two poplar proteins that are most similar to SHI and its closely related gene STYLISH1 (STY1). The two poplar genes are very similar in sequence and expression and are therefore probably paralogs with redundant functions. ? RNAi suppression of the two Populus genes enhanced shoot and root growth, whereas the overexpression of Arabidopsis SHI in poplar reduced internode and petiole length. The suppression of the two genes increased fiber length and the proportion of xylem tissue, mainly through increased xylem cell proliferation. The transgenic modifications were also associated with significant changes in the concentrations of gibberellins and cytokinin. ? We conclude that Populus SHI-RELATED SEQUENCE (SRS) genes play an important role in the regulation of vegetative growth, including wood formation, and thus could be useful tools for the modification of biomass productivity, wood quality or plant form. We studied the effects on plant growth from insertion of five cisgenes that encode proteins involved in gibberellin metabolism or signalling. Intact genomic copies of PtGA20ox7, PtGA2ox2,Pt RGL1_1, PtRGL1_2 and PtGAI1 genes from the genome-sequenced Populus trichocarpa clone Nisqually-1 were transformed into Populus tremula - alba (clone INRA 717-1B4), and growth, morphology and xylem cell size characterized in the greenhouse. Each cisgene encompassed 1-2?kb of 5' and 1?kb of 3' flanking DNA, as well as all native exons and introns. Large numbers of independent insertion events per cisgene (19-38), including empty vector controls, were studied. Three of the cisgenic modifications had significant effects on plant growth rate, morphology or wood properties. The PtGA20ox7 cisgene increased rate of shoot regeneration in vitro, accelerated early growth, and variation in growth rate was correlated with PtGA20ox7 gene expression. PtRGL1_1 and PtGA2ox2 caused reduced growth, while PtRGL1_2 gave rise to plants that grew normally but had significantly longer xylem fibres. RT-PCR studies suggested that the lack of growth inhibition observed in PtRGL1_2 cisgenic plants was a result of co-suppression. PtGAI1 slowed regeneration rate and both PtGAI1 and PtGA20ox7 gave rise to increased variance among events for early diameter and volume index, respectively. Our work suggests that cisgenic insertion of additional copies of native genes involved in growth regulation may provide tools to help modify plant architecture, expand the genetic variance in plant architecture available to breeders and accelerate transfer of alleles between difficult-to-cross species. The role of gibberellins (GAs) in regulation of lateral root development is poorly understood. We show that GA-deficient (35S:PcGA2ox1) and GA-insensitive (35S:rgl1) transgenic Populus exhibited increased lateral root proliferation and elongation under in vitro and greenhouse conditions, and these effects were reversed by exogenous GA treatment. In addition, RNA interference suppression of two poplar GA 2-oxidases predominantly expressed in roots also decreased lateral root formation. GAs negatively affected lateral root formation by inhibiting lateral root primordium initiation. A whole-genome microarray analysis of root development in GA-modified transgenic plants revealed 2069 genes with significantly altered expression. The expression of 1178 genes, including genes that promote cell proliferation, growth, and cell wall loosening, corresponded to the phenotypic severity of the root traits when transgenic events with differential phenotypic expression were compared. The array data and direct hormone measurements suggested crosstalk of GA signaling with other hormone pathways, including auxin and abscisic acid. Transgenic modification of a differentially expressed gene encoding an auxin efflux carrier suggests that GA modulation of lateral root development is at least partly imparted by polar auxin transport modification. These results suggest a mechanism for GA-regulated modulation of lateral root proliferation associated with regulation of plant allometry during the stress response. Here we summarize progress in identification of three classes of genes useful for control of plant architecture: those affecting hormone metabolism and signaling; transcription and other regulatory factors; and the cell cycle. We focus on strong modifiers of stature and form that may be useful for directed modification of plant architecture, rather than the detailed mechanisms of gene action. Gibberellin (GA) metabolic and response genes are particularly attractive targets for manipulation because many act in a dose-dependent manner; similar phenotypic effects can be readily achieved in heterologous species; and induced pleiotropic effects--such as on nitrogen assimilation, photosynthesis, and lateral root production--are usually positive with respect to crop performance. Genes encoding transcription factors represent strong candidates for manipulation of plant architecture. For example, AINTEGUMENTA, ARGOS (auxin-regulated gene controlling organ size), and growth-regulating factors (GRFs) are strong modifiers of leaf and/or flower size. Plants overexpressing these genes had increased organ size and did not display negative pleiotropic effects in glasshouse environments. TCP-domain genes such as CINCINNATA, and the associated regulatory miRNAs such as miRJAW, may provide useful means to modulate leaf curvature and other foliage properties. There are considerable opportunities for comparative and translational genomics in nonmodel plant systems.« less

GPCR6A Is a Molecular Target for the Natural Products Gallate and EGCG in Green Tea.

PubMed

Pi, Min; Kapoor, Karan; Ye, Ruisong; Smith, Jeremy C; Baudry, Jerome; Quarles, Leigh D

2018-04-01

The molecular mechanisms whereby gallates in green tea exert metabolic effects are poorly understood. We found that GPRC6A, a multi-ligand-sensing G-protein-coupled receptor that regulates energy metabolism, sex hormone production, and prostate cancer progression, is a target for gallates. Sodium gallate (SG), gallic acid (GA) > ethyl gallate (EG) > octyl gallate (OG) dose dependently activated ERK in HEK-293 cells transfected with GPRC6A but not in non-transfected controls. SG also stimulated insulin secretion in β-cells isolated from wild-type mice similar to the endogenous GPRC6A ligands, osteocalcin (Ocn) and testosterone (T). Side-chain additions to create OG resulted in loss of GPRC6A agonist activity. Another component of green tea, epigallocatechin 3-gallate (EGCG), dose-dependently inhibited Ocn activation of GPRC6A in HEK-293 cells transfected with GPRC6A and blocked the effect of Ocn in stimulating glucose production in CH10T1/2 cells. Using structural models of the venus fly trap (VFT) and 7-transmembrane (7-TM) domains of GPRC6A, calculations suggest that l-amino acids and GA bind to the VFT, whereas EGCG is calculated to bind to sites in both the VFT and 7-TM. GA and EGCG have offsetting agonist and antagonist effects on GPRC6A that may account for the variable metabolic effect of green tea consumption. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Estimation of endogenous protein and amino acid ileal losses in weaned piglets by regression analysis using diets with graded levels of casein

PubMed Central

2013-01-01

Background Many studies have investigated endogenous loss of proteins and amino acids (AAs) at the ileal level in growing pigs. However, only a few studies have researched this subject in piglets. Knowledge regarding AA ileal digestibility in piglets would be helpful during the formulation of diets for weaning piglets, rather than just using coefficients obtained in growing pigs. Therefore, in this study, we sought to estimate endogenous protein and AA ileal losses in piglets. Furthermore, apparent and true ileal digestibility (AID and TID) of protein and AAs from casein were measured. Results The average flow of protein was 20.8 g/kg of dry matter intake (DMI). Basal protein loss, as estimated by regression, was 16.9 g/kg DMI. Glutamic acid, arginine, and aspartic acid (2.2, 1.4, and 1.2 g/kg DMI, respectively) were the AAs for which greater losses were seen. The AID of protein and AAs increased as the protein level in the diet increased. A higher increment in AID was observed between diets with 80 and160 g CP/kg of feed; this finding was mainly attributable to increases in glycine and arginine (46.1% and 18%, respectively). The TID of protein was 97.8, and the TID of AAs varied from 93.9 for histidine to 100.2 for phenylalanine. Conclusions The basal endogenous protein loss in piglets was 16.9 g/kg DMI. Endogenous protein was rich in glutamic acid, aspartic acid, and arginine, which represented 32.7% of endogenous protein loss in weaning piglets. The TID of casein was high and varied from 93.0 for histidine to 100.2 for phenylalanine. PMID:24053636

Sublattice reversal in GaAs/Ge/GaAs (113)B heterostructures and its application to THz emitting devices based on a coupled multilayer cavity

NASA Astrophysics Data System (ADS)

Lu, Xiangmeng; Kumagai, Naoto; Minami, Yasuo; Kitada, Takahiro

2018-04-01

We fabricated a coupled multilayer cavity with a GaAs/Ge/GaAs sublattice reversal structure for terahertz emission application. Sublattice reversal in GaAs/Ge/GaAs was confirmed by comparing the anisotropic etching profile of an epitaxial sample with those of reference (113)A and (113)B GaAs substrates. The interfaces of GaAs/Ge/GaAs were evaluated at the atomic level by scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDX) mapping. Defect-free GaAs/Ge/GaAs heterostructures were observed in STEM images and the sublattice lattice was directly seen through atomic arrangements in EDX mapping. A GaAs/AlAs coupled multilayer cavity with a sublattice reversal structure was grown on the (113)B GaAs substrate after the confirmation of sublattice reversal. Smooth GaAs/AlAs interfaces were formed over the entire region of the coupled multilayer cavity structure both below and above the Ge layer. Two cavity modes with a frequency difference of 2.9 THz were clearly observed.

Deep levels in osmium doped p-type GaAs grown by metal organic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Iqbal, M. Zafar; Majid, A.; Dadgar, A.; Bimberg, D.

2005-06-01

Results of a preliminary study on deep level transient spectroscopy (DLTS) investigations of osmium (Os) impurity in p-type GaAs, introduced in situ during MOCVD crystal growth, are reported for the first time. Os is clearly shown to introduce two prominent deep levels in the lower half-bandgap of GaAs at energy positions Ev + 0.42 eV (OsA) and Ev + 0.72 eV (OsB). A minority-carrier emitting defect feature observed in the upper half-bandgap is shown to consist of a band of Os-related deep levels with a concentration significantly higher than that of the majority carrier emitting deep levels. Detailed data on the emission rate signatures and related parameters of the Os-related deep levels are reported.

Detecting Fermi-level shifts by Auger electron spectroscopy in Si and GaAs

NASA Astrophysics Data System (ADS)

Debehets, J.; Homm, P.; Menghini, M.; Chambers, S. A.; Marchiori, C.; Heyns, M.; Locquet, J. P.; Seo, J. W.

2018-05-01

In this paper, changes in surface Fermi-level of Si and GaAs, caused by doping and cleaning, are investigated by Auger electron spectroscopy. Based on the Auger voltage contrast, we compared the Auger transition peak energy but with higher accuracy by using a more accurate analyzer and an improved peak position determination method. For silicon, a peak shift as large as 0.46 eV was detected when comparing a cleaned p-type and n-type wafer, which corresponds rather well with the theoretical difference in Fermi-levels. If no cleaning was applied, the peak position did not differ significantly for both wafer types, indicating Fermi-level pinning in the band gap. For GaAs, peak shifts were detected after cleaning with HF and (NH4)2S-solutions in an inert atmosphere (N2-gas). Although the (NH4)2S-cleaning in N2 is very efficient in removing the oxygen from the surface, the observed Ga- and As-peak shifts are smaller than those obtained after the HF-cleaning. It is shown that the magnitude of the shift is related to the surface composition. After Si-deposition on the (NH4)2S-cleaned surface, the Fermi-level shifts back to a similar position as observed for an as-received wafer, indicating that this combination is not successful in unpinning the Fermi-level of GaAs.

THz emission of donor and acceptor doped GaAs/AlGaAs quantum well structures with inserted thin AlAs monolayer

NASA Astrophysics Data System (ADS)

van Dommelen, Paphavee; Daengngam, Chalongrat; Kalasuwan, Pruet

2018-04-01

In this paper, we explore THz range optical intersubband transition energies in a donor doped quantum well of a GaAs/AlGaAs system as a function of the insertion position of an AlAs monolayer in the GaAs quantum well. In simulated models, the optical transition energies between electron subband levels 1 and 2 were higher in the doped structure than in the undoped structure. This may be because the envelope wave function of the second electron subband strongly overlapped the envelope wave function of the first electron subband and influenced the optical intersubband transition between the two levels in the THz range. At different levels of bias voltage at the Schottky barrier on the donor doped structure, the electric field in the growth direction of the structure linearly increased the further away the AlAs monolayer was placed from the reference position. We also simulated the optical transition energies between acceptor energy levels of the acceptor doped structure as a function of the insertion position of the AlAs monolayer. The acceptor doped structure induced THz range emission whereas the undoped structure induced mid-IR emission.

Defect quasi Fermi level control-based CN reduction in GaN: Evidence for the role of minority carriers

NASA Astrophysics Data System (ADS)

Reddy, Pramod; Kaess, Felix; Tweedie, James; Kirste, Ronny; Mita, Seiji; Collazo, Ramon; Sitar, Zlatko

2017-10-01

Compensating point defect reduction in wide bandgap semiconductors is possible by above bandgap illumination based defect quasi Fermi level (dQFL) control. The point defect control technique employs excess minority carriers that influence the dQFL of the compensator, increase the corresponding defect formation energy, and consequently are responsible for point defect reduction. Previous studies on various defects in GaN and AlGaN have shown good agreement with the theoretical model, but no direct evidence for the role of minority carriers was provided. In this work, we provide direct evidence for the role of minority carriers in reducing point defects by studying the predicted increase in work done against defect (CN-1) formation with the decrease in the Fermi level (free carrier concentration) in Si doped GaN at a constant illumination intensity. Comparative defect photoluminescence measurements on illuminated and dark regions of GaN show an excellent quantitative agreement with the theory by exhibiting a greater reduction in yellow luminescence attributed to CN-1 at lower doping, thereby providing conclusive evidence for the role of the minority carriers in Fermi level control-based point defect reduction.

Field-induced strain degradation of AlGaN/GaN high electron mobility transistors on a nanometer scale

NASA Astrophysics Data System (ADS)

Lin, Chung-Han; Doutt, D. R.; Mishra, U. K.; Merz, T. A.; Brillson, L. J.

2010-11-01

Nanoscale Kelvin probe force microscopy and depth-resolved cathodoluminescence spectroscopy reveal an electronic defect evolution inside operating AlGaN/GaN high electron mobility transistors with degradation under electric-field-induced stress. Off-state electrical stress results in micron-scale areas within the extrinsic drain expanding and decreasing in electric potential, midgap defects increasing by orders-of-magnitude at the AlGaN layer, and local Fermi levels lowering as gate-drain voltages increase above a characteristic stress threshold. The pronounced onset of defect formation, Fermi level movement, and transistor degradation at the threshold gate-drain voltage of J. A. del Alamo and J. Joh [Microelectron. Reliab. 49, 1200 (2009)] is consistent with crystal deformation and supports the inverse piezoelectric model of high electron mobility transistor degradation.

Traps in AlGaN /GaN/SiC heterostructures studied by deep level transient spectroscopy

NASA Astrophysics Data System (ADS)

Fang, Z.-Q.; Look, D. C.; Kim, D. H.; Adesida, I.

2005-10-01

AlGaN /GaN/SiC Schottky barrier diodes (SBDs), with and without Si3N4 passivation, have been characterized by temperature-dependent current-voltage and capacitance-voltage measurements, and deep level transient spectroscopy (DLTS). A dominant trap A1, with activation energy of 1.0 eV and apparent capture cross section of 2×10-12cm2, has been observed in both unpassivated and passivated SBDs. Based on the well-known logarithmic dependence of DLTS peak height with filling pulse width for a line-defect related trap, A1, which is commonly observed in thin GaN layers grown by various techniques, is believed to be associated with threading dislocations. At high temperatures, the DLTS signal sometimes becomes negative, likely due to an artificial surface-state effect.

Mg doping of GaN grown by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions

NASA Astrophysics Data System (ADS)

Zhang, Meng; Bhattacharya, Pallab; Guo, Wei; Banerjee, Animesh

2010-03-01

Acceptor doping of GaN with Mg during plasma-assisted molecular beam epitaxy, under N-rich conditions and a relatively high growth temperature of 740 °C, was investigated. The p-doping level steadily increases with increasing Mg flux. The highest doping level achieved, determined from Hall measurements, is 2.1×1018 cm-3. The corresponding doping efficiency and hole mobility are ˜4.9% and 3.7 cm2/V s at room temperature. Cross-sectional transmission electron microscopy and photoluminescence measurements confirm good crystalline and optical quality of the Mg-doped layers. An InGaN/GaN quantum dot light emitting diode (λpeak=529 nm) with p-GaN contact layers grown under N-rich condition exhibits a low series resistance of 9.8 Ω.

Effects of co-exposure to imidacloprid and gibberellic acid on redox status, kidney variables and histopathology in adult rats.

PubMed

Lafi, Bornia; Chaâbane, Mariem; Elwej, Awatef; Grati, Malek; Jamoussi, Kamel; Mnif, Hela; Boudawara, Tahia; Ketata Bouaziz, Hanen; Zeghal, Najiba

2018-05-01

Data on the individual nephrotoxic effects of imidacloprid (IMI) and gibberellic acid (GA 3 ) are scarce. Moreover, there is a lack of information about their combined effects on the renal tissue. Our study investigated the effects of IMI and GA 3 separately or together on rats kidney. IMI (64 mg/kg bw) was given for 3 weeks by gavage either individually or in combination with GA 3 (200 mg/L) via drinking water. IMI associated or no with GA 3 increased the levels of kidney malondialdehyde, advanced oxidation protein products, protein carbonyls and metallothionein, plasma creatinine, urea, blood urea nitrogen and lactate dehydrogenase activity. A decline of kidney uric acid level and antioxidant status was also observed. All these changes were supported by histopathological observations. Our results highlighted the role of IMI and/or GA 3 -induced nephrotoxicity. Co-exposure to IMI and GA 3 exhibited synergism in biochemical kidney variables and histopathology and antagonism in physical and morphological parameters.

Observation of low voltage driven green emission from erbium doped Ga{sub 2}O{sub 3} light-emitting devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zhengwei; Wang, Xu; Zhang, Fabi

Erbium doped Ga{sub 2}O{sub 3} thin films were deposited on Si substrate by pulsed laser deposition method. Bright green emission (∼548 nm) can be observed by naked eye from Ga{sub 2}O{sub 3}:Er/Si light-emitting devices (LEDs). The driven voltage of this LEDs is 6.2 V which is lower than that of ZnO:Er/Si or GaN:Er/Si devices. Since the wide bandgap of Ga{sub 2}O{sub 3} contain more defect-related level which will enhance the effects of recombination between electrons in the defect-related level and the holes in the valence band, resulting in the improvement of the energy transfer to Er ions. We believe that this workmore » paves the way for the development of Si-based green LEDs by using wide bandgap Ga{sub 2}O{sub 3} as the host materials for Er{sup 3+} ions.« less

Correlation of proton irradiation induced threshold voltage shifts to deep level traps in AlGaN/GaN heterostructures

NASA Astrophysics Data System (ADS)

Zhang, Z.; Cardwell, D.; Sasikumar, A.; Kyle, E. C. H.; Chen, J.; Zhang, E. X.; Fleetwood, D. M.; Schrimpf, R. D.; Speck, J. S.; Arehart, A. R.; Ringel, S. A.

2016-04-01

The impact of proton irradiation on the threshold voltage (VT) of AlGaN/GaN heterostructures is systematically investigated to enhance the understanding of a primary component of the degradation of irradiated high electron mobility transistors. The value of VT was found to increase monotonically as a function of 1.8 MeV proton fluence in a sub-linear manner reaching 0.63 V at a fluence of 1 × 1014 cm-2. Silvaco Atlas simulations of VT shifts caused by GaN buffer traps using experimentally measured introduction rates, and energy levels closely match the experimental results. Different buffer designs lead to different VT dependences on proton irradiation, confirming that deep, acceptor-like defects in the GaN buffer are primarily responsible for the observed VT shifts. The proton irradiation induced VT shifts are found to depend on the barrier thickness in a linear fashion; thus, scaling the barrier thickness could be an effective way to reduce such degradation.

Endogenous subclinical hyperthyroidism and cardiovascular system: time to reconsider?

PubMed

Patanè, Salvatore; Marte, Filippo; Sturiale, Mauro

2011-05-19

Subclinical hyperthyroidism is an increasingly recognized entity that is defined as a normal serum free thyroxine and free triiodothyronine levels with a thyroid-stimulating hormone level suppressed below the normal range and usually undetectable. Exogenous sublinical hyperthyroidism is a thyroid metabolic state caused by L-thyroxine administration. Endogenous subclinical hyperthyroidism is a thyroid metabolic state in patients with autonomously functioning thyroid nodule or multinodular goiter, various forms of thyroiditis, in areas with endemic goiter and particularly in elderly subjects. Endogenous subclinical hyperthyroidism is currently the subject of numerous studies and it yet remains controversial particularly as it relates to its treatment and to cardiovascular impact nevertheless established effects have been demonstrated. Recently, acute myocardial infarction without significant coronary stenoses and recurrent acute pulmonary embolism have been reported associated with subclinical hyperthyroidism without L-thyroxine administration. So, it is very important to recognize and to treat promptly also endogenous subclinical hyperthyroidism. Copyright © 2009 Elsevier Ireland Ltd. All rights reserved.

Influence of oral contraceptives on endogenous pain control in healthy women.

PubMed

Rezaii, Taraneh; Ernberg, Malin

2010-06-01

This study investigated the influence of oral contraceptives (OC) on diffuse noxious inhibitory control (DNIC) in healthy women. Fifteen women taking OC and 17 normally menstruating women (No-OC) were tested during high and low endogenous estrogens sessions. Saliva was sampled for analysis of endogenous estradiol level. Mechanical pressure (test stimuli) was applied to the masseter muscle and finger. The pain induced by this pressure was assessed on a 0-10 numerical rating scale (NRS) before, during, and after immersion of the contralateral hand in ice-cold water (cold pressor test, CPT) to induce DNIC. For all subjects, pain induced by the test stimuli decreased significantly during the CPT (P < 0.001). The decrease in general was larger in the No-OC group, with a significant difference between groups in the masseter muscle in the low session (P < 0.027). There were no significant differences between groups or sessions in estradiol levels. These results indicate that endogenous pain modulation may be less effective in OC users.

Assays for endogenous components of human milk: comparison of fresh and frozen samples and corresponding analytes in serum.

PubMed

Hines, Erin P; Rayner, Jennifer L; Barbee, Randy; Moreland, Rae Ann; Valcour, Andre; Schmid, Judith E; Fenton, Suzanne E

2007-05-01

Breast milk is a primary source of nutrition that contains many endogenous compounds that may affect infant development. The goals of this study were to develop reliable assays for selected endogenous breast milk components and to compare levels of those in milk and serum collected from the same mother twice during lactation (2-7 weeks and 3-4 months). Reliable assays were developed for glucose, secretory IgA, interleukin-6, tumor necrosis factor-a, triglycerides, prolactin, and estradiol from participants in a US EPA study called Methods Advancement in Milk Analysis (MAMA). Fresh and frozen (-20 degrees C) milk samples were assayed to determine effects of storage on endogenous analytes. The source effect (serum vs milk) seen in all 7 analytes indicates that serum should not be used as a surrogate for milk in children's health studies. The authors propose to use these assays in studies to examine relationships between the levels of milk components and children's health.

Real-time monitoring of endogenous cysteine levels in living cells using a CD-based ratiometric fluorescent nanoprobe.

PubMed

Wang, Hong; Zhang, Peisheng; Tian, Yong; Zhang, Yuan; Yang, Heping; Chen, Shu; Zeng, Rongjin; Long, Yunfei; Chen, Jian

2018-04-30

A simple and readily available fluorescent probe is needed for the real-time monitoring of endogenous cysteine (Cys) levels in living cells, as such a probe could be used to study the role of Cys in related diseases. Herein, we report the first fluorescent probe based on carbon dots (CDs-FITA) for the selective and ratiometric imaging of endogenous Cys in live cells. In this ratiometric fluorescent probe, a fluorescein derivative (FITA) that recognizes Cys is covalently linked to the surfaces of carbon dots (CDs); employing CDs greatly improves the water solubility of the probe. Acrylate on FITA is selectively cleaved by Cys in aqueous solution under mild conditions, leading to a dramatic increase in the fluorescence from fluorescein. The probe therefore allows the highly selective ratiometric fluorescent detection of Cys even in the presence of various interferents. The as-prepared CDs-FITA showed excellent performance when applied to detect Cys in blood serum. In addition, due to its negligible cytotoxicity, the CDs-FITA can also be utilized for the real-time monitoring of endogenous cysteine (Cys) levels in living cells. Graphical abstract Illustration of the CD-based probe for Cys imaging in living cells.

Diversity of pubertal testosterone changes in boys with constitutional delay in growth and/or adolescence.

PubMed

Kulin, H E; Finkelstein, J W; D'Arcangelo, M R; Susman, E J; Chinchilli, V; Kunselman, S; Schwab, J; Demers, L; Lookingbill, G

1997-01-01

In a group of 22 boys with constitutional delay in growth and/or adolescence, intermittent testosterone enanthate treatment was employed in a randomized clinical trial at multiple doses ranging from 25-100 mg every two weeks for three month periods extending over 15-21 months. Twelve of the patients displayed a prompt increase in endogenous testosterone levels during the study period, reaching levels in the adult male range (> 250 ng/dl). The remaining 10 boys showed sluggish changes in endogenous testosterone during the investigation, ranging from 35-177 ng/dl. The bone ages and testicular sizes of the two groups at study initiation did not differ though urine LH was significantly less at study entry in the slowly maturing group. The data reveal a great diversity in the pace and pattern of endogenous testosterone changes in the study population. The results also suggest that exogenous sex steroid treatment of such patients does not speed up the central nervous system processes controlling the onset and progression of puberty. Boys with delayed puberty should be followed until endogenous testosterone levels reach the adult male range in order to rule out mild gonadotropin deficits.

Physics of Efficiency Droop in GaN:Eu Light-Emitting Diodes.

PubMed

Fragkos, Ioannis E; Dierolf, Volkmar; Fujiwara, Yasufumi; Tansu, Nelson

2017-12-01

The internal quantum efficiency (IQE) of an electrically-driven GaN:Eu based device for red light emission is analyzed in the framework of a current injection efficiency model (CIE). The excitation path of the Eu +3 ion is decomposed in a multiple level system, which includes the carrier transport phenomena across the GaN/GaN:Eu/GaN active region of the device, and the interactions among traps, Eu +3 ions and the GaN host. The identification and analysis of the limiting factors of the IQE are accomplished through the CIE model. The CIE model provides a guidance for high IQE in the electrically-driven GaN:Eu based red light emitters.

Device Performance and Reliability Improvements of AlGaN/GaN/Si MOSFET Using Defect-Free Gate Recess and Laser Annealing

DTIC Science & Technology

2012-07-18

For AlGaN, it is found that Al2O3, Ga2O3 and N-O states were detected on native oxide and HF-treated surfaces. During the course of the ALD process...the N-O bonds are seen to decrease to a level near XPS detection limits, as well as a small decrease in the Ga2O3 concentration, consistent with a...and the other at 1118.2 eV, indicative of a Ga 3+ oxidation state, likely due to Ga2O3 , consistent with previous reports.22,23 There is no evidence

Automated segmentation of geographic atrophy using deep convolutional neural networks

NASA Astrophysics Data System (ADS)

Hu, Zhihong; Wang, Ziyuan; Sadda, SriniVas R.

2018-02-01

Geographic atrophy (GA) is an end-stage manifestation of the advanced age-related macular degeneration (AMD), the leading cause of blindness and visual impairment in developed nations. Techniques to rapidly and precisely detect and quantify GA would appear to be of critical importance in advancing the understanding of its pathogenesis. In this study, we develop an automated supervised classification system using deep convolutional neural networks (CNNs) for segmenting GA in fundus autofluorescene (FAF) images. More specifically, to enhance the contrast of GA relative to the background, we apply the contrast limited adaptive histogram equalization. Blood vessels may cause GA segmentation errors due to similar intensity level to GA. A tensor-voting technique is performed to identify the blood vessels and a vessel inpainting technique is applied to suppress the GA segmentation errors due to the blood vessels. To handle the large variation of GA lesion sizes, three deep CNNs with three varying sized input image patches are applied. Fifty randomly chosen FAF images are obtained from fifty subjects with GA. The algorithm-defined GA regions are compared with manual delineation by a certified grader. A two-fold cross-validation is applied to evaluate the algorithm performance. The mean segmentation accuracy, true positive rate (i.e. sensitivity), true negative rate (i.e. specificity), positive predictive value, false discovery rate, and overlap ratio, between the algorithm- and manually-defined GA regions are 0.97 +/- 0.02, 0.89 +/- 0.08, 0.98 +/- 0.02, 0.87 +/- 0.12, 0.13 +/- 0.12, and 0.79 +/- 0.12 respectively, demonstrating a high level of agreement.

Proton irradiation effects on minority carrier diffusion length and defect introduction in homoepitaxial and heteroepitaxial n-GaN [Proton irradiation effects on minority carrier diffusion length and defect introduction in homoepitaxial n-GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, K. C.; Armstrong, Andrew M.; Allerman, Andrew A.

Here, inherent advantages of wide bandgap materials make GaN-based devices attractive for power electronics and applications in radiation environments. Recent advances in the availability of wafer-scale, bulk GaN substrates have enabled the production of high quality, low defect density GaN devices, but fundamental studies of carrier transport and radiation hardness in such devices are lacking. Here, we report measurements of the hole diffusion length in low threading dislocation density (TDD), homoepitaxial n-GaN, and high TDD heteroepitaxial n-GaN Schottky diodes before and after irradiation with 2.5 MeV protons at fluences of 4–6 × 10 13 protons/cm 2. We also characterize themore » specimens before and after irradiation using electron beam-induced-current (EBIC) imaging, cathodoluminescence, deep level optical spectroscopy (DLOS), steady-state photocapacitance, and lighted capacitance-voltage (LCV) techniques. We observe a substantial reduction in the hole diffusion length following irradiation (50%–55%) and the introduction of electrically active defects which could be attributed to gallium vacancies and associated complexes (V Ga-related), carbon impurities (C-related), and gallium interstitials (Ga i). EBIC imaging suggests long-range migration and clustering of radiation-induced point defects over distances of ~500 nm, which suggests mobile Ga i. Following irradiation, DLOS and LCV reveal the introduction of a prominent optical energy level at 1.9 eV below the conduction band edge, consistent with the introduction of Ga i.« less

Proton irradiation effects on minority carrier diffusion length and defect introduction in homoepitaxial and heteroepitaxial n-GaN [Proton irradiation effects on minority carrier diffusion length and defect introduction in homoepitaxial n-GaN

DOE PAGES

Collins, K. C.; Armstrong, Andrew M.; Allerman, Andrew A.; ...

2017-12-21

Here, inherent advantages of wide bandgap materials make GaN-based devices attractive for power electronics and applications in radiation environments. Recent advances in the availability of wafer-scale, bulk GaN substrates have enabled the production of high quality, low defect density GaN devices, but fundamental studies of carrier transport and radiation hardness in such devices are lacking. Here, we report measurements of the hole diffusion length in low threading dislocation density (TDD), homoepitaxial n-GaN, and high TDD heteroepitaxial n-GaN Schottky diodes before and after irradiation with 2.5 MeV protons at fluences of 4–6 × 10 13 protons/cm 2. We also characterize themore » specimens before and after irradiation using electron beam-induced-current (EBIC) imaging, cathodoluminescence, deep level optical spectroscopy (DLOS), steady-state photocapacitance, and lighted capacitance-voltage (LCV) techniques. We observe a substantial reduction in the hole diffusion length following irradiation (50%–55%) and the introduction of electrically active defects which could be attributed to gallium vacancies and associated complexes (V Ga-related), carbon impurities (C-related), and gallium interstitials (Ga i). EBIC imaging suggests long-range migration and clustering of radiation-induced point defects over distances of ~500 nm, which suggests mobile Ga i. Following irradiation, DLOS and LCV reveal the introduction of a prominent optical energy level at 1.9 eV below the conduction band edge, consistent with the introduction of Ga i.« less

Silencing C19-GA 2-oxidases induces parthenocarpic development and inhibits lateral branching in tomato plants

PubMed Central

Martínez-Bello, Liliam; Moritz, Thomas; López-Díaz, Isabel

2015-01-01

Gibberellins (GAs) are phytohormones that regulate a wide range of developmental processes in plants. Levels of active GAs are regulated by biosynthetic and catabolic enzymes like the GA 2-oxidases (GA2oxs). In tomato (Solanum lycopersicum L.) C19 GA2oxs are encoded by a small multigenic family of five members with some degree of redundancy. In order to investigate their roles in tomato, the silencing of all five genes in transgenic plants was induced. A significant increase in active GA4 content was found in the ovaries of transgenic plants. In addition, the transgenic unfertilized ovaries were much bigger than wild-type ovaries (about 30 times) and a certain proportion (5–37%) were able to develop parthenocarpically. Among the GA2ox family, genes GA2ox1 and -2 seem to be the most relevant for this phenotype since their expression was induced in unfertilized ovaries and repressed in developing fruits, inversely correlating with ovary growth. Interestingly, transgenic lines exhibited a significant inhibition of branching and a higher content of active GA4 in axillary buds. This phenotype was reverted, in transgenic plants, by the application of paclobutrazol, a GA biosynthesis inhibitor, suggesting a role for GAs as repressors of branching. In summary, this work demonstrates that GA 2-oxidases regulate gibberellin levels in ovaries and axillary buds of tomato plants and their silencing is responsible for parthenocarpic fruit growth and branching inhibition. PMID:26093022

GA-optimization for rapid prototype system demonstration

NASA Technical Reports Server (NTRS)

Kim, Jinwoo; Zeigler, Bernard P.

1994-01-01

An application of the Genetic Algorithm (GA) is discussed. A novel scheme of Hierarchical GA was developed to solve complicated engineering problems which require optimization of a large number of parameters with high precision. High level GAs search for few parameters which are much more sensitive to the system performance. Low level GAs search in more detail and employ a greater number of parameters for further optimization. Therefore, the complexity of the search is decreased and the computing resources are used more efficiently.

GaAsP/InGaP HBTs grown epitaxially on Si substrates: Effect of dislocation density on DC current gain

NASA Astrophysics Data System (ADS)

Heidelberger, Christopher; Fitzgerald, Eugene A.

2018-04-01

Heterojunction bipolar transistors (HBTs) with GaAs0.825P0.175 bases and collectors and In0.40Ga0.60P emitters were integrated monolithically onto Si substrates. The HBT structures were grown epitaxially on Si via metalorganic chemical vapor deposition, using SiGe compositionally graded buffers to accommodate the lattice mismatch while maintaining threading dislocation density at an acceptable level (˜3 × 106 cm-2). GaAs0.825P0.175 is used as an active material instead of GaAs because of its higher bandgap (increased breakdown voltage) and closer lattice constant to Si. Misfit dislocation density in the active device layers, measured by electron-beam-induced current, was reduced by making iterative changes to the epitaxial structure. This optimized process culminated in a GaAs0.825P0.175/In0.40Ga0.60P HBT grown on Si with a DC current gain of 156. By considering the various GaAsP/InGaP HBTs grown on Si substrates alongside several control devices grown on GaAs substrates, a wide range of threading dislocation densities and misfit dislocation densities in the active layers could be correlated with HBT current gain. The effect of threading dislocations on current gain was moderated by the reduction in minority carrier lifetime in the base region, in agreement with existing models for GaAs light-emitting diodes and photovoltaic cells. Current gain was shown to be extremely sensitive to misfit dislocations in the active layers of the HBT—much more sensitive than to threading dislocations. We develop a model for this relationship where increased base current is mediated by Fermi level pinning near misfit dislocations.

The QTL GNP1 Encodes GA20ox1, Which Increases Grain Number and Yield by Increasing Cytokinin Activity in Rice Panicle Meristems.

PubMed

Wu, Yuan; Wang, Yun; Mi, Xue-Fei; Shan, Jun-Xiang; Li, Xin-Min; Xu, Jian-Long; Lin, Hong-Xuan

2016-10-01

Cytokinins and gibberellins (GAs) play antagonistic roles in regulating reproductive meristem activity. Cytokinins have positive effects on meristem activity and maintenance. During inflorescence meristem development, cytokinin biosynthesis is activated via a KNOX-mediated pathway. Increased cytokinin activity leads to higher grain number, whereas GAs negatively affect meristem activity. The GA biosynthesis genes GA20oxs are negatively regulated by KNOX proteins. KNOX proteins function as modulators, balancing cytokinin and GA activity in the meristem. However, little is known about the crosstalk among cytokinin and GA regulators together with KNOX proteins and how KNOX-mediated dynamic balancing of hormonal activity functions. Through map-based cloning of QTLs, we cloned a GA biosynthesis gene, Grain Number per Panicle1 (GNP1), which encodes rice GA20ox1. The grain number and yield of NIL-GNP1TQ were significantly higher than those of isogenic control (Lemont). Sequence variations in its promoter region increased the levels of GNP1 transcripts, which were enriched in the apical regions of inflorescence meristems in NIL-GNP1TQ. We propose that cytokinin activity increased due to a KNOX-mediated transcriptional feedback loop resulting from the higher GNP1 transcript levels, in turn leading to increased expression of the GA catabolism genes GA2oxs and reduced GA1 and GA3 accumulation. This rebalancing process increased cytokinin activity, thereby increasing grain number and grain yield in rice. These findings uncover important, novel roles of GAs in rice florescence meristem development and provide new insights into the crosstalk between cytokinin and GA underlying development process.

Response of single junction GaAs/GaAs and GaAs/Ge solar cells to multiple doses of 1 MeV electrons

NASA Technical Reports Server (NTRS)

Meier, D. L.; Szedon, J. R.; Bartko, J.; Chung, M. A.

1989-01-01

A comparison of the radiation tolerance of MOCVD-grown GaAs cells and GaAs/Ge cells was undertaken using 1 MeV electrons. The GaAs/Ge cells are somewhat more tolerant of 1 MeV electron irradiation and more responsive to annealing than are the GaAs/GaAs cells examined in this study. However, both types of cells suffer a greater degradation in efficiency than has been observed in other recent studies. The reason for this is not certain, but it may be associated with an emitter thickness which appears to be greater than desired. The deep level transient spectroscopy (DLTS) spectra following irradiation are not significantly different for the GaAs/Ge and the GaAs/GaAs cells, with each having just two peaks. The annealing behavior of these peaks is also similar in the two samples examined. It appears that no penalty in radiation tolerance, and perhaps some benefit, is associated with fabricating MOCVD GaAs cells on Ge substrates rather than GaAs substrates.

Dual nature of acceptors in GaN and ZnO: The curious case of the shallow MgGa deep state

NASA Astrophysics Data System (ADS)

Lany, Stephan; Zunger, Alex

2010-04-01

Employing a Koopmans corrected density functional method, we find that the metal-site acceptors Mg, Be, and Zn in GaN and Li in ZnO bind holes in deep levels that are largely localized at single anion ligand atoms. In addition to this deep ground state (DGS), we observe an effective-masslike delocalized state that can exist as a short lived shallow transient state (STS). The Mg dopant in GaN represents the unique case where the ionization energy of the localized deep level exceeds only slightly that of the shallow effective-mass acceptor, which explains why Mg works so exceptionally well as an acceptor dopant.

Optical signatures of deep level defects in Ga2O3

NASA Astrophysics Data System (ADS)

Gao, Hantian; Muralidharan, Shreyas; Pronin, Nicholas; Karim, Md Rezaul; White, Susan M.; Asel, Thaddeus; Foster, Geoffrey; Krishnamoorthy, Sriram; Rajan, Siddharth; Cao, Lei R.; Higashiwaki, Masataka; von Wenckstern, Holger; Grundmann, Marius; Zhao, Hongping; Look, David C.; Brillson, Leonard J.

2018-06-01

We used depth-resolved cathodoluminescence spectroscopy and surface photovoltage spectroscopy to measure the effects of near-surface plasma processing and neutron irradiation on native point defects in β-Ga2O3. The near-surface sensitivity and depth resolution of these optical techniques enabled us to identify spectral changes associated with removing or creating these defects, leading to identification of one oxygen vacancy-related and two gallium vacancy-related energy levels in the β-Ga2O3 bandgap. The combined near-surface detection and processing of Ga2O3 suggests an avenue for identifying the physical nature and reducing the density of native point defects in this and other semiconductors.

Generalized Anxiety and Major Depressive syndrome ...

EPA Pesticide Factsheets

Objective: Environmental exposure to manganese (Mn) may cause generalized anxiety (GA) and major depression (MD) in residents living in Mn-exposed areas. Marietta and East Liverpool are two Ohio towns identified as having elevated levels of Mn. The objective was to determine if levels of Mn exposure were associated with levels of GA and MD.Participants and methods: 186 participants (Mean age: 55.0 ± 10.80) were examined. Levels of air-Mn were assessed over a period of ten years using U.S. EPA’s AERMOD dispersion model. Average air-Mn exposure was 0.53 μg/m3 in the two towns. The GA syndrome was comprised of anxiety, obsessive-compulsive, and phobic scales from the Symptom Checklist (SCL-90-R). The MD syndrome was comprised of depression, anxiety, and psychoticism scales also from the SCL-90-R. Linear regression models were used to determine the relationship between Mn and GA, MD and the specific components of each.Results: Elevated air-Mn was associated with GA (β= 0.240, p=0.002), and MD (β= 0.202, p=0.011). Air-Mn was associated with specific components of GA anxiety (β= 0.255, p=0.001), phobic anxiety (β= 0.159, p=0.046), and obsessive-compulsive (β= 0.197, p=0.013). Similarly, components of MD syndrome suggested an association as well: depression (β= 0.180, p=0.023), anxiety (β= 0.255, p=0.001), and psychoticism (β= 0.188, p=0.018). Conclusions: The results suggest that residents with elevated exposure to environmental Mn have elevated levels of

Impact of glatiramer acetate on paraclinical markers of neuroprotection in multiple sclerosis: A prospective observational clinical trial.

PubMed

Ehling, Rainer; Di Pauli, Franziska; Lackner, Peter; Rainer, Carolyn; Kraus, Viktoria; Hegen, Harald; Lutterotti, Andreas; Kuenz, Bettina; De Zordo, Tobias; Schocke, Michael; Glatzl, Susanne; Löscher, Wolfgang N; Deisenhammer, Florian; Reindl, Markus; Berger, Thomas

2015-10-15

Data from in vitro and animal studies support a neuroprotective role of glatiramer acetate (GA) in multiple sclerosis (MS). We investigated prospectively whether treatment with GA leads to clinical and paraclinical changes associated with neuroprotection in patients with relapsing-remitting (RR) MS. Primary aim of this clinical study was to determine serum BDNF levels in RR-MS patients who were started on GA as compared to patients who remained therapy-naive throughout 24 months. Secondary outcomes included relapses and EDSS, cognition, quality of life, fatigue and depression, BDNF expression levels on peripheral immune cells (FACS, RT-PCR), serum anti-myelin basic peptide (MBP) antibody status, evoked potential and cerebral MRI studies. While GA treatment did not alter serum levels or expression levels on peripheral immune cells of BDNF over time it resulted in a transient increase of serum IgG antibody response to MBP, mainly due to subtype IgG1 (p<0.05), after 3 months. However, no significant differences were found between GA treated and therapy-naive patients with regard to serum BDNF and intracellular BDNF expression levels, nerve conduction (including median and tibial nerve somatosensory, pattern-shift visual and upper and lower limb motor evoked potentials) or MRI (including volume of hyperintense lesions, volume of hypointense lesions after CE, mean diffusivity and fractional anisotropy) outcome parameters. In conclusion, our findings do not support a major impact of GA treatment on paraclinical markers of neuroprotection in human RR-MS. Copyright © 2015 Elsevier B.V. All rights reserved.

Near-UV emission from In-rich InGaN/GaN single quantum well structure with compositional grading

NASA Astrophysics Data System (ADS)

Kwon, S.-Y.; Cho, M.-H.; Moon, P.; Kim, H. J.; Na, H.; Seo, H.-C.; Kim, H. J.; Shin, Y.; Moon, D. W.; Sun, Y.; Cho, Y.-H.; Yoon, E.

2004-09-01

We grew high quality In-rich InGaN/GaN single quantum well (SQW) structures by metal-organic chemical vapor deposition using growth interruption and obtained a sharp photoluminescence peak in near-ultraviolet (UV) region. During In-rich InGaN well layer growth, only TMIn and ammonia were supplied, however, atomic interdiffusion as well as defect generation occurred to relieve large lattice mismatch over 10% between InN and GaN. From medium-energy ion scattering measurement and subsequent fitting of the spectrum, we could find that the InGaN well layer was In-rich and it has 60-70% indium content. We also found the compositional grading of indium at top and bottom InGaN/GaN interfaces. The Fourier series method was used to calculate the energy levels and envelope functions in In-rich InGaN/GaN SQW with compositional grading and we could quantitatively explain the near-UV emission observed from the SQW.

Laser diode bars based on strain-compensated AlGaPAs/GaAs heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marmalyuk, Aleksandr A; Ladugin, M A; Yarotskaya, I V

2012-01-31

Traditional (in the AlGaAs/GaAs system) and phosphorus-compensated (in the AlGaAs/AlGaPAs/GaAs system) laser heterostructures emitting at a wavelength of 850 nm are grown by MOVPE and studied. Laser diode bars are fabricated and their output characteristics are studied. The method used to grow heterolayers allowed us to control (minimise) mechanical stresses in the AlGaPAs/GaAs laser heterostructure, which made it possible to keep its curvature at the level of the initial curvature of the substrate. It is shown that the use of a compensated AlGaPAs/GaAs heterostructure improves the linear distribution of emitting elements in the near field of laser diode arrays andmore » allows the power - current characteristic to retain its slope at high pump currents owing to a uniform contact of all emitting elements with the heat sink. The radius of curvature of the grown compensated heterostructures turns out to be smaller than that of traditional heterostructures.« less

Lightweight concentrator module with 30 percent AM0 efficient GaAs/GaSb tandem cells

NASA Technical Reports Server (NTRS)

Avery, J. E.; Fraas, L. M.; Sundaram, V. S.; Mansoori, N.; Yerkes, J. W.; Brinker, D. J.; Curtis, H. B.; O'Neill, M. J.

1990-01-01

A concept is presented for an aerospace concentrator module with lightweight domed lenses and 30 percent AM0 efficient GaAs/GaSb tandem solar cell circuits. The performance of transparent GaAs cells is reviewed. NASA's high-altitude jet flight calibration data for recent GaSb cells assembled with bulk GaAs filters are reported, along with subsequent Boeing and NASA measurements of GaSb I-V performance at various light levels and temperatures. The expected performance of a basic two-terminal tandem concentrator circuit with three-to-one voltage matching is discussed. All of the necessary components being developed to assemble complete flight test coupons are shown. Straightforward interconnect and assembly techniques yield voltage matched circuits with near-optimum performance over a wide temperature range.

Restricted cell elongation in Arabidopsis hypocotyls is associated with a reduced average pectin esterification level

PubMed Central

Derbyshire, Paul; McCann, Maureen C; Roberts, Keith

2007-01-01

Background Cell elongation is mainly limited by the extensibility of the cell wall. Dicotyledonous primary (growing) cell walls contain cellulose, xyloglucan, pectin and proteins, but little is known about how each polymer class contributes to the cell wall mechanical properties that control extensibility. Results We present evidence that the degree of pectin methyl-esterification (DE%) limits cell growth, and that a minimum level of about 60% DE is required for normal cell elongation in Arabidopsis hypocotyls. When the average DE% falls below this level, as in two gibberellic acid (GA) mutants ga1-3 and gai, and plants expressing pectin methyl-esterase (PME1) from Aspergillus aculeatus, then hypocotyl elongation is reduced. Conclusion Low average levels of pectin DE% are associated with reduced cell elongation, implicating PMEs, the enzymes that regulate DE%, in the cell elongation process and in responses to GA. At high average DE% other components of the cell wall limit GA-induced growth. PMID:17572910

Restricted cell elongation in Arabidopsis hypocotyls is associated with a reduced average pectin esterification level.

PubMed

Derbyshire, Paul; McCann, Maureen C; Roberts, Keith

2007-06-17

Cell elongation is mainly limited by the extensibility of the cell wall. Dicotyledonous primary (growing) cell walls contain cellulose, xyloglucan, pectin and proteins, but little is known about how each polymer class contributes to the cell wall mechanical properties that control extensibility. We present evidence that the degree of pectin methyl-esterification (DE%) limits cell growth, and that a minimum level of about 60% DE is required for normal cell elongation in Arabidopsis hypocotyls. When the average DE% falls below this level, as in two gibberellic acid (GA) mutants ga1-3 and gai, and plants expressing pectin methyl-esterase (PME1) from Aspergillus aculeatus, then hypocotyl elongation is reduced. Low average levels of pectin DE% are associated with reduced cell elongation, implicating PMEs, the enzymes that regulate DE%, in the cell elongation process and in responses to GA. At high average DE% other components of the cell wall limit GA-induced growth.

Transparent conductive oxide films mixed with gallium oxide nanoparticle/single-walled carbon nanotube layer for deep ultraviolet light-emitting diodes

PubMed Central

2013-01-01

We propose a transparent conductive oxide electrode scheme of gallium oxide nanoparticle mixed with a single-walled carbon nanotube (Ga2O3 NP/SWNT) layer for deep ultraviolet light-emitting diodes using spin and dipping methods. We investigated the electrical, optical and morphological properties of the Ga2O3 NP/SWNT layers by increasing the thickness of SWNTs via multiple dipping processes. Compared with the undoped Ga2O3 films (current level 9.9 × 10-9 A @ 1 V, transmittance 68% @ 280 nm), the current level flowing in the Ga2O3 NP/SWNT increased by approximately 4 × 105 times and the transmittance improved by 9% after 15 times dip-coating (current level 4 × 10-4 A at 1 V; transmittance 77.0% at 280 nm). These improvements result from both native high transparency of Ga2O3 NPs and high conductivity and effective current spreading of SWNTs. PMID:24295342

Dietary acid, age, and serum bicarbonate levels among adults in the United States.

PubMed

Amodu, Afolarin; Abramowitz, Matthew K

2013-12-01

Greater dietary acid has been associated with lower serum bicarbonate levels in patients with CKD. Whether this association extends to the general population and if it is modified by age are unknown. This study examined the association of the dietary acid load, estimated by net endogenous acid production, with serum bicarbonate levels in adult participants in the National Health and Nutrition Examination Survey 1999-2004. The mean serum bicarbonate was 24.9 mEq/L (SEM=0.1), and the mean estimated net endogenous acid production was 57.4 mEq/d (SEM=0.4). Serum bicarbonate was linearly associated with age, such that the oldest participants had the highest serum bicarbonate levels. After multivariable adjustment, participants in the highest quartile of net endogenous acid production had 0.40 mEq/L (95% confidence interval, -0.55 to -0.26) lower serum bicarbonate and a 33% (95% confidence interval, 3 to 72) higher likelihood of acidosis compared with those participants in the lowest quartile. There was a significant interaction by age of the association of net endogenous acid production with serum bicarbonate (P=0.005). Among participants 20-39, 40-59, and ≥60 years old, those participants in the highest net endogenous acid production quartile had 0.26 (95% confidence interval, -0.49 to -0.03), 0.60 (95% confidence interval, -0.92 to -0.29), and 0.49 (95% confidence interval, -0.84 to -0.14) mEq/L lower serum bicarbonate, respectively, compared with participants in the lowest quartile. Greater dietary acid is associated with lower serum bicarbonate in the general US population, and the magnitude of this association is greater among middle-aged and elderly persons than younger adults.

On a direct connection of the transition metal impurity levels to the band edge discontinuities in semiconductor heterojunctions

NASA Astrophysics Data System (ADS)

Langer, Jerzy M.; Heinrich, Helmut

1985-11-01

Our recent proposal of using the transition metal impurity levels to predict the isovalent heterojunction (HJ) band-edge discontinuities is further discussed. It is shown that for Ga 1-xAl xAs/GaAs heterojunctions most of the recent discontinuity data follow within experimental error the prediction of the ΔE cb: ΔE vb= 0.64:0.36 discontinuity ratio derived from the Fe 2+ level position in Ga 1-xAl xAs compound. Predictions of valence-band discontinuities for the other III-V and II-VI HJ systems are also given.

[Changes in polyamine levels in Citrus sinensis Osb. cv. Valencia callus during somatic embryogenesis].

PubMed

Liu, Hua-Ying; Xiao, Lang-Tao; Lu, Xu-Dong; Hu, Jia-Jin; Wu, Shun; He, Chang-Zheng; Deng, Xiu-Xin

2005-06-01

Somatic embryogenetic capability and changes in polyamine level and their relationship were analyzed using the long-term (8 years) subcultured calli of Citrus sinensis Osb. cv. Valencia as materials. The results showed that endogenous polyamine contents in embryogenic calli were higher than those in non-embryogenic calli, and the embryogenetic capability was positively correlated to the levels of endogenous polyamines. When the calli were transferred to a differentiation medium, the putrescine content rapidly increased and reached a peak, then fell gradually. Applying exogenous putrescine raised the embryogenesis frequency and endogenous putrescine level. It indicated that increase in putrescine content at early stage of differentiation promoted embryogenesis. With the development of somatic embryo, spermidine content reached its the highest level at globular embryo stage, spermine content rose and reached a peak at a later stage of globular embryo development. Furthermore, changes of the putrescine, spermidine and spermine contents during somatic embryogenesis were similar in Valencia calli which had different ploidy levels, but their contents decreased following the increasing of ploidy level. Changes in arginine decarboxylase activity were positively correlated to the polyamine levels, which suggest that the later is a key factor in regulating the polyamine levels during somatic embryogenesis in citrus plants.

Nanoparticle mediated brain targeted delivery of gallic acid: in vivo behavioral and biochemical studies for improved antioxidant and antidepressant-like activity.

PubMed

Nagpal, Kalpana; Singh, Shailendra Kumar; Mishra, Dina Nath

2012-11-01

Gallic acid had been reported to possess antidepressant like activity, which may be attributed to its CNS effects like increase in reduced glutathione levels, increased catalase activity and decreased malonaldehyde levels in brain. This study was designed to enhance the antidepressant-like activity of gallic acid (GA) using nanoparticulate delivery system in swiss male albino mice and to explore the possible underlying mechanisms for this activity. GA loaded chitosan nanoparticles (GANP) and corresponding tween 80 coated batch (cGANP) were formulated for brain targeting of GA and characterized for physicochemical parameters, morphology, differential scanning calorimetry and in vitro drug release. GA, GANP, cGANP (dose equivalent to GA 10 mg/kg, i.p.) and positive control drug, Fluoxetine (10 mg/kg, i.p.) were administered for successive seven days to male swiss albino mice. Then, the in vivo antidepressant-like activity was evaluated using Despair Swim Test (DST) and Tail Suspension Test (TST); along with the evaluation of MAO-A activity, reduced glutathione, malonaldehyde level, catalase and locomotor activity in mice. KEYFINDINGS: cGANP (equivalent to 10 mg/kg, i.p.) significantly decreased immobility period of mice in DST and TST, indicating significant antidepressant-like activity. There was no significant effect on locomotor activity of the mice by GA and its nanoparticle formulations. cGANP (10 mg/kg, i.p.) significantly decreased Monoamine oxidase-A (MAO-A) activity, malondialdehyde levels, and catalase activity in mice. GA possess significant antidepressant like activity and ligand coated nanoparticle approach with improved brain targeting may serve as an effective approach to enhance such effect.

Comparing the Effects of Combined General/Epidural Anaesthesia and General Anaesthesia on Serum Cytokine Levels in Radical Cystectomy

PubMed Central

Karadeniz, Meltem Savran; Mammadov, Orkhan; Çiftci, Hayriye Şentürk; Usta, Sebahat Akgül; Pembeci, Kamil

2017-01-01

Objective Surgical stress combined with general anaesthesia (GA) suppresses the immune system and leads to cancer cell growth and premature metastasis in major oncological interventions. Epidural analgesia decreases the need for inhalation agents and opioids during surgery by suppressing sympathetic and neuroendocrine responses in the postoperative period. This study aimed to compare the effects of combined general/epidural anaesthesia (GEA)+patient-controlled epidural analgesia (PCEA) and GA+IV patient-controlled analgesia (PCA) on serum tumour necrosis factor-alpha TNF-α), interleukin-1 beta (IL-1β) and interferon-gamma (IFN-γ) levels in patients undergoing radical cystectomy. Methods Sixty-five patients were enrolled in this prospective study. Patients were randomly enrolled to the GEA group, i.e., combined GEA+ PCEA (0.1% bupivacaine+1 μg mL−1 fentanyl), and the GA group, namely combined GA+IV PCA (0.03 mg mL−1 morphine). To evaluate the cytokine response, blood samples were collected at preoperative, postoperative 1st and 24th hours. Results There was no statistically significant difference in serum TNF-α, IL-1β and IFN-γ levels between groups GA and GEA at preoperative and postoperative 1st hour and 24th hour. Total remifentanil consumption was significantly lower and length of hospital stay was significantly shorter in the GEA group than in the GA group (p<0.05). Conclusion There is no difference between two anaesthesia methods in terms of serum cytokine levels; however, combined GEA+PCEA technique appeared to be superior to GA+IV PCA because of lower intraoperative narcotic analgesic consumption and shorter hospital stay. PMID:28868167

Dissection of Arabidopsis NCED9 promoter regulatory regions reveals a role for ABA synthesized in embryos in the regulation of GA-dependent seed germination.

PubMed

Seo, Mitsunori; Kanno, Yuri; Frey, Anne; North, Helen M; Marion-Poll, Annie

2016-05-01

Nine-cis-epoxycarotenoid dioxygenase (NCED) catalyzes the key step of abscisic acid (ABA) biosynthesis. There are five genes encoding NCED in Arabidopsis, which differentially regulate ABA biosynthesis in a spatiotemporal manner in response to endogenous and environmental stimuli. Previous studies have shown that NCED9 is expressed in testa and embryos during seed development. In the present study, we have identified promoter regions required for the expression of NCED9 in testa and embryos, respectively. Electrophoretic mobility shift assays (EMSA) and yeast one-hybrid (Y1H) assays showed that several homeodomain-leucine zipper (HD-Zip) proteins, namely ATHBs, bound to the sequence required for expression of NCED9 in testa, suggesting that they redundantly regulate NCED9 expression. By expressing the NCED9 gene under the control of a deleted NCED9 promoter in an nced9 mutant expression was limited to embryos. Transformants were complemented for the paclobutrazol resistant germination phenotype of the mutant, suggesting that the ABA synthesis mediated by NCED9 in embryos plays an important role in the regulation of gibberellin (GA)-dependent seed germination. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Atomic-scale structure and electronic properties of GaN/GaAs superlattices

NASA Astrophysics Data System (ADS)

Goldman, R. S.; Feenstra, R. M.; Briner, B. G.; O'Steen, M. L.; Hauenstein, R. J.

1996-12-01

We have investigated the atomic-scale structure and electronic properties of GaN/GaAs superlattices produced by nitridation of a molecular beam epitaxially grown GaAs surface. Using cross-sectional scanning tunneling microscopy (STM) and spectroscopy, we show that the nitrided layers are laterally inhomogeneous, consisting of groups of atomic-scale defects and larger clusters. Analysis of x-ray diffraction data in terms of fractional area of clusters (determined by STM), reveals a cluster lattice constant similar to bulk GaN. In addition, tunneling spectroscopy on the defects indicates a conduction band state associated with an acceptor level of NAs in GaAs. Therefore, we identify the clusters and defects as nearly pure GaN and NAs, respectively. Together, the results reveal phase segregation in these arsenide/nitride structures, in agreement with the large miscibility gap predicted for GaAsN.

Exogenous agmatine has neuroprotective effects against restraint-induced structural changes in the rat brain

PubMed Central

Zhu, Meng-Yang; Wang, Wei-Ping; Cai, Zheng-Wei; Regunathan, Soundar; Ordway, Gregory

2009-01-01

Agmatine is an endogenous amine derived from decarboxylation of arginine catalysed by arginine decarboxylase. Agmatine is considered a novel neuromodulator and possesses neuroprotective properties in the central nervous system. The present study examined whether agmatine has neuroprotective effects against repeated restraint stress-induced morphological changes in rat medial prefrontal cortex and hippocampus. Sprague-Dawley rats were subjected to 6 h of restraint stress daily for 21 days. Immunohistochemical staining with β-tubulin III showed that repeated restraint stress caused marked morphological alterations in the medial prefrontal cortex and hippocampus. Stress-induced alterations were prevented by simultaneous treatment with agmatine (50 mg/kg/day, i.p.). Interestingly, endogenous agmatine levels, as measured by high-performance liquid chromatography, in the prefrontal cortex and hippocampus as well as in the striatum and hypothalamus of repeated restraint rats were significantly reduced as compared with the controls. Reduced endogenous agmatine levels in repeated restraint animals were accompanied by a significant increase of arginine decarboxylase protein levels in the same regions. Moreover, administration of exogenous agmatine to restrained rats abolished increases of arginine decarboxylase protein levels. Taken together, these results demonstrate that exogenously administered agmatine has neuroprotective effects against repeated restraint-induced structural changes in the medial prefrontal cortex and hippocampus. These findings indicate that stress-induced reductions in endogenous agmatine levels in the rat brain may play a permissive role in neuronal pathology induced by repeated restraint stress. PMID:18364017

Elevating Endogenous GABA Levels with GAT-1 Blockade Modulates Evoked but Not Induced Responses in Human Visual Cortex

PubMed Central

Muthukumaraswamy, Suresh D; Myers, Jim F M; Wilson, Sue J; Nutt, David J; Hamandi, Khalid; Lingford-Hughes, Anne; Singh, Krish D

2013-01-01

The electroencephalographic/magnetoencephalographic (EEG/MEG) signal is generated primarily by the summation of the postsynaptic currents of cortical principal cells. At a microcircuit level, these glutamatergic principal cells are reciprocally connected to GABAergic interneurons. Here we investigated the relative sensitivity of visual evoked and induced responses to altered levels of endogenous GABAergic inhibition. To do this, we pharmacologically manipulated the GABA system using tiagabine, which blocks the synaptic GABA transporter 1, and so increases endogenous GABA levels. In a single-blinded and placebo-controlled crossover study of 15 healthy participants, we administered either 15 mg of tiagabine or a placebo. We recorded whole-head MEG, while participants viewed a visual grating stimulus, before, 1, 3 and 5 h post tiagabine ingestion. Using beamformer source localization, we reconstructed responses from early visual cortices. Our results showed no change in either stimulus-induced gamma-band amplitude increases or stimulus-induced alpha amplitude decreases. However, the same data showed a 45% reduction in the evoked response component at ∼80 ms. These data demonstrate that, in early visual cortex the evoked response shows a greater sensitivity compared with induced oscillations to pharmacologically increased endogenous GABA levels. We suggest that previous studies correlating GABA concentrations as measured by magnetic resonance spectroscopy to gamma oscillation frequency may reflect underlying variations such as interneuron/inhibitory synapse density rather than functional synaptic GABA concentrations. PMID:23361120

Orientation independence of heterojunction-band offsets at GaAs-AlAs heterointerfaces characterized by x-ray photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Hirakawa, K.; Hashimoto, Y.; Ikoma, T.

1990-12-01

We systematically studied the orientation and the growth sequence dependence of the valence-band offset ΔEv at the lattice-matched common anion GaAs-AlAs interfaces. High quality GaAs-AlAs heterojunctions were carefully grown on GaAs substrates with three major orientations, namely, (100), (110), and (111)B. The core level energy distance ΔECL between Ga 3d and Al 2p levels was measured by in situ x-ray photoemission spectroscopy. ΔECL is found to be independent of the substrate orientation and the growth sequence, which clearly indicates the face independence of ΔEv. This result suggests that the band lineup at lattice-matched isovalent semiconductor heterojunctions is determined by the bulk properties of the constituent materials. ΔEv is determined to be 0.44 ± 0.05 eV.

Increase in the Shockley–Read–Hall recombination rate in InGaN/GaN QWs as the main mechanism of the efficiency droop in LEDs at high injection levels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bochkareva, N. I.; Rebane, Yu. T.; Shreter, Yu. G., E-mail: y.shreter@mail.ioffe.ru

It is shown that the efficiency droop observed as the current through a GaN-based light-emitting diode increases is due to a decrease in the Shockley–Read–Hall nonradiative lifetime. The lifetime decreases with increasing current because a steadily growing number of traps in the density-of-states tails of InGaN/GaN quantum wells become nonradiative recombination centers upon the approach of quasi-Fermi levels to the band edges. This follows from the correlation between the efficiency droop and the appearance of negative differential capacitance, observed in the study. The correlation appears due to slow trap recharging via the trap-assisted tunneling of electrons through the n-type barriermore » of the quantum well and to the inductive nature of the diode-current variation with forward bias.« less

Application of the bounds-analysis approach to arsenic and gallium antisite defects in gallium arsenide

DOE PAGES

Wright, A. F.; Modine, N. A.

2015-01-23

The As antisite in GaAs (AsGa) has been the subject of numerous experimental and theoretical studies. Recent density-functional-theory (DFT) studies report results in good agreement with experimental data for the +2, +1, and 0 charge states of the stable EL2 structure, the 0 charge state of the metastable EL2* structure, and the activation energy to transform from EL2* to EL2 in the 0 charge state. However, these studies did not report results for EL2* in the -1 charge state. In this paper, we report new DFT results for the +2, +1, 0, and -1 charge states of AsGa, obtained usingmore » a semilocal exchange-correlation functional and interpreted using a bounds-analysis approach. In good agreement with experimental data, we find a -1/0 EL2* level 0.06 eV below the conduction-band edge and an activation energy of 0.05 eV to transform from EL2* to EL2 in the -1 charge state. While the Ga antisite in GaAs (GaAs) has not been studied as extensively as AsGa, experimental studies report three charge states (-2, -1, 0) and two levels (-2/-1, -1/0) close to the valence-band edge. Recent DFT studies report the same charge states, but the levels are found to be well-separated from the valence-band edge. To resolve this disagreement, we performed new DFT calculations for GaAs and interpreted them using a bounds analysis. The analysis identified the -1 and 0 charge states as hole states weakly bound to a highly-localized -2 charge state. Moreover, the -2/-1, -1/0 levels were found to be near the valence-band edge, in good agreement with the experimental data.« less

Defect properties of InGaAsN layers grown as sub-monolayer digital alloys by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Baranov, Artem I.; Gudovskikh, Alexander S.; Kudryashov, Dmitry A.; Lazarenko, Alexandra A.; Morozov, Ivan A.; Mozharov, Alexey M.; Nikitina, Ekaterina V.; Pirogov, Evgeny V.; Sobolev, Maxim S.; Zelentsov, Kirill S.; Egorov, Anton Yu.; Darga, Arouna; Le Gall, Sylvain; Kleider, Jean-Paul

2018-04-01

The defect properties of InGaAsN dilute nitrides grown as sub-monolayer digital alloys (SDAs) by molecular beam epitaxy for photovoltaic application were studied by space charge capacitance spectroscopy. Alloys of i-InGaAsN (Eg = 1.03 eV) were lattice-matched grown on GaAs wafers as a superlattice of InAs/GaAsN with one monolayer of InAs (<0.5 nm) between wide GaAsN (7-12 nm) layers as active layers in single-junction solar cells. Low p-type background doping was demonstrated at room temperature in samples with InGaAsN layers 900 nm and 1200 nm thick (less 1 × 1015 cm-3). According to admittance spectroscopy and deep-level transient spectroscopy measurements, the SDA approach leads to defect-free growth up to a thickness of 900 nm. An increase in thickness to 1200 nm leads to the formation of non-radiative recombination centers with an activation energy of 0.5 eV (NT = 8.4 × 1014 cm-3) and a shallow defect level at 0.20 eV. The last one leads to the appearance of additional doping, but its concentration is low (NT = 5 × 1014 cm-3) so it does not affect the photoelectric properties. However, further increase in thickness to 1600 nm, leads to significant growth of its concentration to (3-5) × 1015 cm-3, while the concentration of deep levels becomes 1.3 × 1015 cm-3. Therefore, additional free charge carriers appearing due to ionization of the shallow level change the band diagram from p-i-n to p-n junction at room temperature. It leads to a drop of the external quantum efficiency due to the effect of pulling electric field decrease in the p-n junction and an increased number of non-radiative recombination centers that negatively impact lifetimes in InGaAsN.

Orientation-dependent surface core-level shifts and chemical shifts on clean and H 2S-covered GaAs

NASA Astrophysics Data System (ADS)

Ranke, W.; Finster, J.; Kuhr, H. J.

1987-08-01

Photoelectron spectra of the As 3d and Ga 3d core levels were studied in situ on a cylindrically shaped GaAs single crystal for the six inequivalent orientations (001), (113), (111), (110), (11¯1) and (11¯3). On the clean surface, prepared by molecular beam epitaxy (MBE), surface core levels are shifted by 0.25 to 0.55 eV towards smaller binding energy (BE) for As 3d and -0.25 to -0.35 eV towards higher BE for Ga, depending on orientation. Additional As causes As 3d contributions shifted between -0.45 and -0.7 eV towards higher BE. The position and intensity of them is influenced by H 2S adsorption. At 150 K, H 2S adsorbs preferentially on As sites. As chemical shifts appear at -0.6 to -0.9 eV towards higher BE. Simultaneously, As accumulation occurs on all orientations with the exception of (110). High temperature adsorption (550 K, 720 K) influences mainly the Ga 3d peaks. Two peaks shifted by about -0.45 and -0.8 eV towards higher Be were found which are attributed to Ga atoms with one or two sulfur ligands, respectively. At 720 K, also As depletion is observed. The compatibility of surface core-level positions and intensities with recent structural models for the (111) and (11¯1) surfaces is discussed.

Atypical titration curves for GaAl12 Keggin-ions explained by a joint experimental and simulation approach

NASA Astrophysics Data System (ADS)

Sulpizi, Marialore; Lützenkirchen, Johannes

2018-06-01

Although they have been widely used as models for oxide surfaces, the deprotonation behaviors of the Keggin-ions (MeAl127+) and typical oxide surfaces are very different. On Keggin-ions, the deprotonation occurs over a very narrow pH range at odds with the broad charging curve of larger oxide surfaces. Depending on the Me concentration, the deprotonation curve levels off sooner (high Me concentration) or later (for low Me concentration). The leveling off shows the onset of aggregation before which the Keggin-ions are present as individual units. We show that the atypical titration data previously observed for some GaAl12 solutions in comparison to the originally reported data can be explained by the presence of Ga2Al11 ions. The pKa value of aquo-groups bound to octahedral Ga was determined from ab initio molecular dynamics simulations relative to the pure GaAl12 ions. Using these results within a surface complexation model, the onset of deprotonation of the crude solution is surprisingly well predicted and the ratio between the different species is estimated to be in the proportion 20 (Ga2Al11) : 20 (Al13) : 60 (GaAl12).

Comparison of trap characteristics between AlGaN/GaN and AlGaN/InGaN/GaN heterostructure by frequency dependent conductance measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, Apurba, E-mail: apurba.chakraborty86@gmail.com; Biswas, Dhrubes; Advanced Technology Development Centre, IIT Kharagpur, Kharagpur 721302

2015-02-23

Frequency dependent conductance measurement is carried out to observe the trapping effect in AlGaN/InGaN/GaN double heterostructure and compared that with conventional AlGaN/GaN single heterostructure. It is found that the AlGaN/InGaN/GaN diode structure does not show any trapping effect, whereas single heterostructure AlGaN/GaN diode suffers from two kinds of trap energy states in near depletion to higher negative voltage bias region. This conductance behaviour of AlGaN/InGaN/GaN heterostructure is owing to more Fermi energy level shift from trap energy states at AlGaN/InGaN junction compare to single AlGaN/GaN heterostructure and eliminates the trapping effects. Analysis yielded interface trap energy state in AlGaN/GaN ismore » to be with time constant of (33.8–76.5) μs and trap density of (2.38–0.656) × 10{sup 12 }eV{sup −1} cm{sup −2} in −3.2 to −4.8 V bias region, whereas for AlGaN/InGaN/GaN structure no interface energy states are found and the extracted surface trap energy concentrations and time constants are (5.87–4.39) ×10{sup 10} eV{sup −1} cm{sup −2} and (17.8–11.3) μs, respectively, in bias range of −0.8–0.0 V.« less

Ga flux dependence of Er-doped GaN luminescent thin films

NASA Astrophysics Data System (ADS)

Lee, D. S.; Steckl, A. J.

2002-02-01

Er-doped GaN thin films have been grown on (111) Si substrates with various Ga fluxes in a radio frequency plasma molecular beam epitaxy system. Visible photoluminescence (PL) and electroluminescence (EL) emission at 537/558 nm and infrared (IR) PL emission at 1.5 μm from GaN:Er films exhibited strong dependence on the Ga flux. Both visible and IR PL and visible EL increase with the Ga flux up to the stoichiometric growth condition, as determined by growth rate saturation. Beyond this condition, all luminescence levels abruptly dropped to the detection limit with increasing Ga flux. The Er concentration, measured by secondary ion mass spectroscopy and Rutherford backscattering, decreases with increasing Ga flux under N-rich growth conditions and remains constant above the stoichiometric growth condition. X-ray diffraction indicated that the crystalline quality of the GaN:Er film was improved with increasing Ga flux up to stoichiometric growth condition and then saturated. Er ions in the films grown under N-rich conditions appear much more optically active than those in the films grown under Ga-rich conditions.

Impacts of Carrier Transport and Deep Level Defects on Delayed Cathodoluminescence in Droop-Mitigating InGaN/GaN LEDs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Zhibo; Singh, Akshay; Chesin, Jordan

Prevalent droop mitigation strategies in InGaN-based LEDs require structural and/or compositional changes in the active region but are accompanied by a detrimental reduction in external quantum efficiency (EQE) due to increased Shockley-Read-Hall recombination. Understanding the optoelectronic impacts of structural modifications in InGaN/GaN quantum wells (QW) remains critical for emerging high-power LEDs. In this work, we use a combination of electron microscopy tools along with standard electrical characterization to investigate a wide range of low-droop InGaN/GaN QW designs. We find that chip-scale EQE is uncorrelated with extended well-width fluctuations observed in scanning transmission electron microscopy. Further, we observe delayed cathodoluminescence (CL)more » response from designs in which calculated band profiles suggest facile carrier escape from individual QWs. Samples with the slowest CL responses also exhibit the lowest EQEs and highest QW defect densities in deep level optical spectroscopy. We propose a model in which the electron beam (i) passivates deep level defect states and (ii) drives charge carrier accumulation and subsequent reduction of the built-in field across the multi-QW active region, resulting in delayed radiative recombination. Finally, we correlate CL rise dynamics with capacitance-voltage measurements and show that certain early-time components of the CL dynamics reflect the open circuit carrier population within one or more QWs.« less

Slow Replication Fork Velocity of Homologous Recombination-Defective Cells Results from Endogenous Oxidative Stress.

PubMed

Wilhelm, Therese; Ragu, Sandrine; Magdalou, Indiana; Machon, Christelle; Dardillac, Elodie; Técher, Hervé; Guitton, Jérôme; Debatisse, Michelle; Lopez, Bernard S

2016-05-01

Replications forks are routinely hindered by different endogenous stresses. Because homologous recombination plays a pivotal role in the reactivation of arrested replication forks, defects in homologous recombination reveal the initial endogenous stress(es). Homologous recombination-defective cells consistently exhibit a spontaneously reduced replication speed, leading to mitotic extra centrosomes. Here, we identify oxidative stress as a major endogenous source of replication speed deceleration in homologous recombination-defective cells. The treatment of homologous recombination-defective cells with the antioxidant N-acetyl-cysteine or the maintenance of the cells at low O2 levels (3%) rescues both the replication fork speed, as monitored by single-molecule analysis (molecular combing), and the associated mitotic extra centrosome frequency. Reciprocally, the exposure of wild-type cells to H2O2 reduces the replication fork speed and generates mitotic extra centrosomes. Supplying deoxynucleotide precursors to H2O2-exposed cells rescued the replication speed. Remarkably, treatment with N-acetyl-cysteine strongly expanded the nucleotide pool, accounting for the replication speed rescue. Remarkably, homologous recombination-defective cells exhibit a high level of endogenous reactive oxygen species. Consistently, homologous recombination-defective cells accumulate spontaneous γH2AX or XRCC1 foci that are abolished by treatment with N-acetyl-cysteine or maintenance at 3% O2. Finally, oxidative stress stimulated homologous recombination, which is suppressed by supplying deoxynucleotide precursors. Therefore, the cellular redox status strongly impacts genome duplication and transmission. Oxidative stress should generate replication stress through different mechanisms, including DNA damage and nucleotide pool imbalance. These data highlight the intricacy of endogenous replication and oxidative stresses, which are both evoked during tumorigenesis and senescence initiation, and emphasize the importance of homologous recombination as a barrier against spontaneous genetic instability triggered by the endogenous oxidative/replication stress axis.

Mild Staphylococcus aureus Skin Infection Improves the Course of Subsequent Endogenous S. aureus Bacteremia in Mice

PubMed Central

van den Berg, Sanne; de Vogel, Corné P.; van Belkum, Alex; Bakker-Woudenberg, Irma A. J. M.

2015-01-01

Staphylococcus aureus carriers with S. aureus bacteremia may have a reduced mortality risk compared to non-carriers. A role for the immune system is suggested. Here, we study in mice the effect of mild S. aureus skin infection prior to endogenous or exogenous S. aureus bacteremia, and evaluate protection in relation to anti-staphylococcal antibody levels. Skin infections once or twice by a clinical S. aureus isolate (isolate P) or S. aureus strain 8325-4 were induced in mice free of S. aureus and anti-staphylococcal antibodies. Five weeks later, immunoglobulin G (IgG) levels in blood against 25 S. aureus antigens were determined, and LD50 or LD100 bacteremia caused by S. aureus isolate P was induced. S. aureus skin infections led to elevated levels of anti-staphylococcal IgG in blood. One skin infection improved the course of subsequent severe endogenous bacteremia only. A second skin infection further improved animal survival rate, which was associated with increased pre-bacteremia IgG levels against Efb, IsaA, LukD, LukE, Nuc, PrsA and WTA. In conclusion, S. aureus isolate P skin infection in mice reduces the severity of subsequent endogenous S. aureus bacteremia only. Although cellular immune effects cannot be rules out, anti-staphylococcal IgG against specified antigens may contribute to this effect. PMID:26060995

Investigation of endogenous soybean food allergens by using a 2-dimensional gel electrophoresis approach.

PubMed

Rouquié, David; Capt, Annabelle; Eby, William H; Sekar, Vaithilingam; Hérouet-Guicheney, Corinne

2010-12-01

As part of the safety assessment of genetically modified (GM) soybean, 2-dimensional gel electrophoresis analyses were performed with the isoxaflutole and glyphosate tolerant soybean FG72, its non-GM near-isogenic counterpart (Jack) and three commercial non-GM soybean lines. The objective was to compare the known endogenous human food allergens in seeds in the five different soybean lines in order to evaluate any potential unintended effect(s) of the genetic modification. In total, 37 protein spots representing five well known soybean food allergen groups were quantified in each genotype. Qualitatively, all the allergenic proteins were detected in the different genetic backgrounds. Quantitatively, among 37 protein spots, the levels of accumulation of three allergens were slightly lower in the GM soybean than in the non-GM counterparts. Specifically, while the levels of two of these three allergens fell within the normal range of variation observed in the four non-GM varieties, the level of the third allergen was slightly below the normal range. Overall, there was no significant increase in the level of allergens in FG72 soybean seeds. Therefore, the FG72 soybean can be considered as safe as its non-GM counterpart with regards to endogenous allergenicity. Additional research is needed to evaluate the biological variability in the levels of endogenous soybean allergens and the correlation between level of allergens and allergenic potential in order to improve the interpretation of these data in the safety assessment of GM soybean context. Copyright © 2010 Elsevier Inc. All rights reserved.

Low dose of L-glutamic acid attenuated the neurological dysfunctions and excitotoxicity in bilateral common carotid artery occluded mice.

PubMed

Ramanathan, Muthiah; Abdul, Khadar K; Justin, Antony

2016-10-01

Glutamate, an excitatory neurotransmitter in the brain, produces excitotoxicity through its agonistic action on postsynaptic N-methyl-D-aspartate receptor, resulting in neurodegeneration. We hypothesized that the administration of low doses of glutamate in cerebral ischemia could attenuate the excitotoxicity in neurons through its autoreceptor regulatory mechanism, and thereby control neurodegeneration. To test the hypothesis, the effect of L-glutamic acid (L-GA) 400 μmol/l/kg was evaluated in a bilateral common carotid artery occlusion-induced global ischemic mouse model. Memantine was used as a positive control. Global ischemia in mice was induced by occlusion of both the common carotid artery (bilateral common carotid artery occlusion) for 20 min, followed by reperfusion injury. L-GA was infused slowly through the tail vein 30 min before the surgery and every 24 h thereafter until the end of the experiment. The time-dependent change in cerebral blood flow was monitored using a laser Doppler image analyzer. The neurotransmitters glutamate and γ-aminobutyric acid (GABA) and the neurobiochemicals ATP, glutathione, and nitric oxide were measured in the different regions of brain at 0, 24, 48, and 72 h after reperfusion injury. L-GA increased locomotor activity, muscle coordination, and cerebral blood flow in ischemic mice at 72 h after ischemic insult. L-GA reduced glutamate levels in the cortex, striatum, and hippocampus at 72 h, whereas GABA levels were elevated in all three brain regions studied. Further, L-GA elevated glutathione levels and attenuated nitric oxide levels, but failed to restore ATP levels 72 h after ischemia-reperfusion. We conclude that the gradual reduction of glutamate along with elevation of GABA in different brain regions could have contributed toward the neuroprotective effect of L-GA. Hence, a slow infusion of a low dose of L-GA could be beneficial in controlling excitotoxicity-induced neurodegeneration following ischemia.

Game-based peripheral biofeedback for stress assessment in children.

PubMed

Pop-Jordanova, Nada; Gucev, Zoran

2010-06-01

Peripheral biofeedback is considered to be an efficient method for assessment and stress mitigation in children. The aim of the present study was to assess the levels of stress and stress mitigation in healthy school children (HSC), in children with cystic fibrosis (CF), general anxiety (GA) and attention-deficit-hyperactivity disorder (ADHD). Each investigated group (HSC, CF, GA, ADHD) consisted of 30 school-aged children from both sexes. Psychological characteristics were evaluated on Eysenck Personality Questionnaire (EPQ). The lie scale was used to determine participant honesty. Four biofeedback games using a pulls detector were applied for assessment of the stress levels as well as to evaluate ability to relax. EPQ found more psychopathological traits (P < 0.001) and less extroversion (P < 0.001) in children with GA and ADHD. In addition, high neurotic tendencies were found in children with CF (P < 0.01) and GA (P < 0.01). Unexpectedly, the lie scale was lower in ADHD children (P < 0.01) than in all other groups (HSC, CF, GA). The Magic blocks score was significantly different in relaxation levels between control and CF children (P < 0.05). Speed in the game Canal was significantly different in relaxation levels between healthy controls and all other groups, but no changes in pulls, as a relaxation measure, were found during the game. The CF group had much more commissions stemming from impulsivity (t= 5.71, P < 0.01), while the GA and ADHD children had more inattention omissions (P < 0.05). Strong negative correlation between age and pulls (r= 0.49, P= 0.003) and strong negative correlation between age and omissions (r=-0.86, P= 0.029) were found among all groups analyzed. The ability to learn stress mediation is correlated with age. All three groups of children had significantly lower relaxation levels when compared to healthy controls. Relaxation was more difficult for children with GA or ADHD, and easier for children with CF.

Early histological, hormonal, and molecular changes during pineapple (Ananas comosus (L.) Merrill) artificial flowering induction.

PubMed

Espinosa, Maita Eulalia Ávila; Moreira, Rafael Oliveira; Lima, André Almeida; Ságio, Solange Aparecida; Barreto, Horllys Gomes; Luiz, Sara Lazara Pérez; Abreu, Carlos Eduardo Aragón; Yanes-Paz, Ermis; Ruíz, Yanelis Capdesuñer; González-Olmedo, Justo Lorenzo; Chalfun-Júnior, Antonio

2017-02-01

Natural flowering can cause serious scheduling problems in the pineapple (Ananas comosus) industry and increase harvest costs. Pineapple flowering is thought to be triggered by increased ethylene levels and artificial forcing of pineapple flowering is a common practice to promote flowering synchronisation. However, little is known about the early hormonal and molecular changes of pineapple flowering induction and development. Here, we aimed to analyse the molecular, hormonal, and histological changes during artificial pineapple flowering by Ethrel ® 48 treatment. Histological analyses of the shoot apical meristem, leaf gibberellic acid (GA 3 ), and ethylene quantification were carried out during the first 72h after Ethrel ® 48 treatment. Expression profiles from ethylene biosynthesis (AcACS2 and AcACO1), gibberellin metabolism (AcGA2-ox1 and AcDELLA1), and flower development (FT-like gene (AcFT), LFY-like gene (AcLFY), and a PISTILLATA-like gene (AcPI)) genes were analysed during the first 24h after Ethrel ® 48 treatment. Differentiation processes of the shoot apical meristem into flower buds were already present in the first 72h after Ethrel ® 48 treatment. Ethrel ® 48 lead to a reduction in GA 3 levels, probably triggered by elevated ethylene levels and the positive regulation AcGA2-ox1. AcLFY activation upon Ethrel ® 48 may also have contributed to the reduction of GA 3 levels and, along with the up-regulation of AcPI, are probably associated with the flower induction activation. AcFT and AcDELLA1 do not seem to be regulated by GA 3 and ethylene. Decreased GA 3 and increased ethylene levels suggest an accumulation of AcDELLA1, which may display an important role in pineapple flowering induction. Thus, this study shows that molecular, hormonal, and histological changes are present right after Ethrel ® 48 treatment, providing new insights into how pineapple flowering occurs under natural conditions. Copyright © 2016 Elsevier GmbH. All rights reserved.

Oral contraceptives cause evolutionarily novel increases in hormone exposure

PubMed Central

Lovett, Jennie L; Chima, Margo A; Wexler, Juliana K; Arslanian, Kendall J; Friedman, Andrea B; Yousif, Chantal B; Strassmann, Beverly I

2017-01-01

Abstract Background and objectives In the evolutionary past, women spent most of their reproductive lives either pregnant or in lactational amenorrhea, and rarely menstruated. The current pattern of frequent menses, and the associated increase in endogenous hormonal exposure, has been implicated in the current breast cancer epidemic. It is not known, however, whether oral contraceptives further increase, or actually decrease, hormonal exposure over one menstrual cycle. Here, we examined variation in hormonal exposure across seven oral contraceptive (OC) formulations, and produced the first quantitative comparison of exogenous versus endogenous hormone exposure. Methodology Data from 12 studies of serum estradiol (E2) and progesterone (P4) were aggregated to create a composite graph of endogenous hormone levels over one menstrual cycle in European or American women (age 19–40 years). Pharmacokinetic package insert data, also from Western women, were used to calculate exposures for hormones in seven different OC formulations. Endogenous and exogenous hormone levels were compared after adjusting for the relative binding affinity (RBA) of progestin to the progesterone receptor and ethinyl estradiol (EE) to the estrogen receptor. Results After adjusting for RBA, median ethinyl estradiol exposure across 28 days in the OCs was 11.4 nmol/l, similar to median E2 exposure. One formulation, however, was 40% higher in ethinyl estradiol exposure relative to median endogenous estradiol. Median exposure from progestins in OCs (1496 nmol/l) was 4-fold higher than the median endogenous exposure from P4 (364 nmol/l). Exposure from OC progestins ranged from one sixtieth to 8-fold median endogenous P4 over 28 days. Conclusions and implications Given that breast cancer risk increases with hormonal exposure, our finding that four widely prescribed formulations more than quadruple progestin exposure relative to endogenous progesterone exposure is cause for concern. As not all formulations produce the same exposures, these findings are pertinent to contraceptive choice. We also identify critical gaps in the provision of relevant data on pharmacokinetics and carcinogenicity by drug manufacturers. PMID:28685096

Laser cooling of BH and GaF: insights from an ab initio study.

PubMed

Gao, Yu-feng; Gao, Tao

2015-04-28

The feasibility of laser cooling BH and GaF is investigated using ab initio quantum chemistry. The ground state X (1)Σ(+) and first two excited states (3)Π and (1)Π of BH and GaF are calculated using the multireference configuration interaction (MRCI) level of theory. For GaF, the spin-orbit coupling effect is also taken into account in the electronic structure calculations at the MRCI level. Calculated spectroscopic constants for BH and GaF show good agreement with available theoretical and experimental results. The highly diagonal Franck-Condon factors (BH: f00 = 0.9992, f11 = 0.9908, f22 = 0.9235; GaF: f00 = 0.997, f11 = 0.989, f22 = 0.958) for the (1)Π (v' = 0-2) → X (1)Σ(+) (v = 0-2) transitions in BH and GaF are determined, which are found to be in good agreement with the theoretical and experimental data. Radiative lifetime calculations of the (1)Π (v' = 0-2) state (BH: 131, 151, and 187 ns; GaF: 2.26, 2.36, and 2.48 ns) are found to be short enough for rapid laser cooling. The proposed laser cooling schemes that drive the (1)Π (v' = 0) → X (1)Σ(+) (v = 0) transition use just one laser wavelength λ00 (BH: 436 nm, GaF: 209 nm). Though the cooling wavelength of GaF is deep in the UVC, a frequency quadrupled Ti:sapphire laser (189-235 nm) could be capable of generating useful quantities of light at this wavelength. The present results indicate that BH and GaF are two good choices of molecules for laser cooling.

Molecular cloning and characterization of a novel tomato xylosyltransferase specific for gentisic acid.

PubMed

Tárraga, Susana; Lisón, Purificación; López-Gresa, María Pilar; Torres, Cristina; Rodrigo, Ismael; Bellés, José María; Conejero, Vicente

2010-10-01

The importance of salicylic acid (SA) in the signal transduction pathway of plant disease resistance has been well documented in many incompatible plant-pathogen interactions, but less is known about signalling in compatible interactions. In this type of interaction, tomato plants have been found to accumulate high levels of 2,5-dihydroxybenzoic acid (gentisic acid, GA), a metabolic derivative of SA. Exogenous GA treatments induce in tomato plants a set of PR proteins that differ from those induced by salicylic acid. While SA accumulates in tomato plants mainly as 2-O-β-D-glucoside, GA has only been found as 5-O-β-D-xyloside. To characterize this step of the GA signalling pathway further, the present work focuses on the study of the GA-conjugating activity in tomato plants. A gentisate glycosyltransferase (GAGT) cDNA has been isolated and overexpressed in Pichia pastoris, and GA-conjugating activity was confirmed by detecting the xylosylated GA. The purified plant protein is highly specific for GA, showing no activity toward many other phenolic compounds, including SA. In addition, it shows an outstanding selectivity for UDP-xylose as the sugar donor, which differentiates this enzyme from most glycosyltransferases. Both the GA-conjugating activity and the corresponding mRNA show a strong, rapid, and transient induction upon treatment of tomato plants with GA or SA. Furthermore, its expression is rapidly induced by compatible infections. However, neither the gene nor the activity seems to respond to incompatible infections or wounding. The unique properties of this new glycosyltransferase suggest a specific role in regulating the free GA levels in compatible plant-pathogen interactions.

Influence of InGaN sub-quantum-well on performance of InAlN/GaN/InAlN resonant tunneling diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Haoran; Yang, Lin'an, E-mail: layang@xidian.edu.cn; Hao, Yue

The resonant tunneling mechanism of the GaN based resonant tunneling diode (RTD) with an InGaN sub-quantum-well has been investigated by means of numerical simulation. At resonant-state, Electrons in the InGaN/InAlN/GaN/InAlN RTD tunnel from the emitter region through the aligned discrete energy levels in the InGaN sub-quantum-well and GaN main-quantum-well into the collector region. The implantation of the InGaN sub-quantum-well alters the dominant transport mechanism, increase the transmission coefficient and give rise to the peak current and peak-to-valley current ratio. We also demonstrate that the most pronounced negative-differential-resistance characteristic can be achieved by choosing appropriately the In composition of In{sub x}Ga{submore » 1−x}N at around x = 0.06.« less

Carrier concentration dependence of donor activation energy in n-type GaN epilayers grown on Si (1 1 1) by plasma-assisted MBE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Mahesh; Central Research Laboratory, Bharat Electronics, Bangalore 560 013; Bhat, Thirumaleshwara N.

Highlights: ► The n-type GaN layers were grown by plasma-assisted molecular beam epitaxy. ► The optical characteristics of a donor level in Si-doped GaN were studied. ► Activation energy of a Si-related donor was estimated from temperature dependent PL measurements. ► PL peak positions, FWHM of PL and activation energies are found to be proportional to the cube root of carrier density. ► The involvement of donor levels is supported by the temperature-dependent electron concentration measurements. -- Abstract: The n-type GaN layers were grown by plasma-assisted MBE and either intentionally doped with Si or unintentionally doped. The optical characteristics ofmore » a donor level in Si-doped, GaN were studied in terms of photoluminescence (PL) spectroscopy as a function of electron concentration. Temperature dependent PL measurements allowed us to estimate the activation energy of a Si-related donor from temperature-induced decay of PL intensity. PL peak positions, full width at half maximum of PL and activation energies are found to be proportional to the cube root of carrier density. The involvement of donor levels is supported by the temperature-dependent electron concentration measurements.« less

Reward can modulate attentional capture, independent of top-down set.

PubMed

Munneke, Jaap; Hoppenbrouwers, Sylco S; Theeuwes, Jan

2015-11-01

The traditional distinction between exogenous and endogenous attentional control has recently been enriched with an additional mode of control, termed "selection history." Recent findings have indicated, for instance, that previously rewarded or punished stimuli capture more attention than their physical attributes would predict. As such, the value that is associated with certain stimuli modulates attentional capture. This particular influence has also been shown for endogenous attention. Although recent leads have emerged, elucidating the influences of reward on exogenous and endogenous attention, it remains unclear to what extent exogenous attention is modulated by reward when endogenous attention is already deployed. We used a Posner cueing task in which exogenous and endogenous cues were presented to guide attention. Crucially, the exogenous cue also indicated the reward value. That is, the color of the exogenous cue indicated how much reward could be obtained on a given trial. The results showed main effects of endogenous and exogenous attention (i.e., speeded reaction times when either cue was valid, as compared to when it was invalid). Crucially, an interaction between exogenous cue validity and reward level was observed, indicating that reward-based associative-learning processes rapidly influence attentional capture, even when endogenous attention has been actively deployed.

Lattice damage and compositional changes in Xe ion irradiated InxGa1-xN (x = 0.32-1.0) single crystals

DOE PAGES

Zhang, Limin; Jiang, Weilin; Dissanayake, Amila C.; ...

2016-06-27

Lattice disorder and compositional changes in InxGa1-xN (x=0.32, 0.47, 0.7, 0.8 and 1.0) films on GaN/Al2O3 substrates, induced by room-temperature irradiation of 5 MeV Xe ions, have been investigated using both Rutherford backscattering spectrometry under ion-channeling conditions and time-of-flight secondary ion mass spectrometry. The results show that for a fluence of 3E13 cm-2, the relative level of lattice disorder in InxGa1-xN increases monotonically from 59% to 90% with increasing indium concentration x from 0.32 to 0.7; a further increase in x up to 1.0 leads to little increase in the disorder level. In contrast to Ga-rich InxGa1-xN (x=0.32 and 0.47),more » significant volume swelling of up to ~25% accompanied with oxidation in In-rich InxGa1-xN (x=0.7, 0.8 and 1.0) is observed. In addition, irradiation-induced atomic mixing occurs at the interface of In-rich InxGa1-xN and GaN. The results from this study indicate an extreme susceptibility of the high In-content InxGa1-xN to heavy-ion irradiation, and suggest that cautions must be exercised in applying ion-implantation techniques to these materials at room temperature. Further studies of the irradiation behavior at elevated temperatures are warranted.« less

Temperature and intensity dependence of the performance of an electron-irradiated (AlGa)As/GaAs solar cell

NASA Technical Reports Server (NTRS)

Swartz, C. K.; Hart, R. E., Jr.

1979-01-01

The performance of a Hughes, liquid-phase epitaxial 2 centimeter-by-2 centimeter, (AlGa)As/GaAs solar cell was measured before and after irradiations with 1 MeV electrons to fluences of 1 x 10 to the 16th power electrons/sq cm. The temperature dependence of performance was measured over the temperature range 135 to 415 K at each fluence level. In addition, temperature dependences were measured at five intensity levels from 137 to 2.57 mW/sq cm before irradiation and after a fluence of 1 x 10 to the 16th power electrons/sq cm. For the intermediate fluences, performance was measured as a function of intensity at 298 K only.

Endophytic Bacterium Pseudomonas fluorescens RG11 May Transform Tryptophan to Melatonin and Promote Endogenous Melatonin Levels in the Roots of Four Grape Cultivars

PubMed Central

Ma, Yaner; Jiao, Jian; Fan, Xiucai; Sun, Haisheng; Zhang, Ying; Jiang, Jianfu; Liu, Chonghuai

2017-01-01

Endophytes have been verified to synthesize melatonin in vitro and promote abiotic stress-induced production of endogenous melatonin in grape (Vitis vinifera L.) roots. This study aimed to further characterize the biotransformation of tryptophan to melatonin in the endophytic bacterium Pseudomonas fluorescens RG11 and to investigate its capacity for enhancing endogenous melatonin levels in the roots of different grape cultivars. Using ultra performance liquid chromatography-tandem mass spectrometry combined with 15N double-labeled L-tryptophan as the precursor for melatonin, we detected isotope-labeled 5-hydroxytryptophan, serotonin, N-acetylserotonin, and melatonin, but tryptamine was not detected during the in vitro incubation of P. fluorescens RG11. Furthermore, the production capacity of these four compounds peaked during the exponential growth phase. RG11 colonization increased the endogenous levels of 5-hydroxytryptophan, N-acetylserotonin, and melatonin, but reduced those of tryptamine and serotonin, in the roots of the Red Globe grape cultivar under salt stress conditions. Quantitative real-time PCR revealed that RG11 reduced the transcription of grapevine tryptophan decarboxylase and serotonin N-acetyltransferase genes when compared to the un-inoculated control. These results correlated with decreased reactive oxygen species bursts and cell damage, which were alleviated by RG11 colonization under salt stress conditions. Additionally, RG11 promoted plant growth and enhanced the levels of endogenous melatonin in different grape cultivars. Intraspecific variation in the levels of melatonin precursors was found among four grape cultivars, and the associated root crude extracts appeared to significantly induce RG11 melatonin biosynthesis in vitro. Overall, this study provides useful information that enhances the existing knowledge of a potential melatonin synthesis pathway in rhizobacteria, and it reveals plant–rhizobacterium interactions that affect melatonin biosynthesis in plants subjected to abiotic stress conditions. PMID:28119731

Endophytic Bacterium Pseudomonas fluorescens RG11 May Transform Tryptophan to Melatonin and Promote Endogenous Melatonin Levels in the Roots of Four Grape Cultivars.

PubMed

Ma, Yaner; Jiao, Jian; Fan, Xiucai; Sun, Haisheng; Zhang, Ying; Jiang, Jianfu; Liu, Chonghuai

2016-01-01

Endophytes have been verified to synthesize melatonin in vitro and promote abiotic stress-induced production of endogenous melatonin in grape ( Vitis vinifera L.) roots. This study aimed to further characterize the biotransformation of tryptophan to melatonin in the endophytic bacterium Pseudomonas fluorescens RG11 and to investigate its capacity for enhancing endogenous melatonin levels in the roots of different grape cultivars. Using ultra performance liquid chromatography-tandem mass spectrometry combined with 15N double-labeled L -tryptophan as the precursor for melatonin, we detected isotope-labeled 5-hydroxytryptophan, serotonin, N -acetylserotonin, and melatonin, but tryptamine was not detected during the in vitro incubation of P. fluorescens RG11. Furthermore, the production capacity of these four compounds peaked during the exponential growth phase. RG11 colonization increased the endogenous levels of 5-hydroxytryptophan, N -acetylserotonin, and melatonin, but reduced those of tryptamine and serotonin, in the roots of the Red Globe grape cultivar under salt stress conditions. Quantitative real-time PCR revealed that RG11 reduced the transcription of grapevine tryptophan decarboxylase and serotonin N -acetyltransferase genes when compared to the un-inoculated control. These results correlated with decreased reactive oxygen species bursts and cell damage, which were alleviated by RG11 colonization under salt stress conditions. Additionally, RG11 promoted plant growth and enhanced the levels of endogenous melatonin in different grape cultivars. Intraspecific variation in the levels of melatonin precursors was found among four grape cultivars, and the associated root crude extracts appeared to significantly induce RG11 melatonin biosynthesis in vitro . Overall, this study provides useful information that enhances the existing knowledge of a potential melatonin synthesis pathway in rhizobacteria, and it reveals plant-rhizobacterium interactions that affect melatonin biosynthesis in plants subjected to abiotic stress conditions.

Structural and electronic properties of isovalent boron atoms in GaAs

NASA Astrophysics Data System (ADS)

Krammel, C. M.; Nattermann, L.; Sterzer, E.; Volz, K.; Koenraad, P. M.

2018-04-01

Boron containing GaAs, which is grown by metal organic vapour phase epitaxy, is studied at the atomic level by cross-sectional scanning tunneling microscopy (X-STM) and spectroscopy (STS). In topographic X-STM images, three classes of B related features are identified, which are attributed to individual B atoms on substitutional Ga sites down to the second layer below the natural {110} cleavage planes. The X-STM contrast of B atoms below the surface reflects primarily the structural modification of the GaAs matrix by the small B atoms. However, B atoms in the cleavage plane have in contrast to conventional isovalent impurities, such as Al and In, a strong influence on the local electronic structure similar to donors or acceptors. STS measurements show that B in the GaAs {110} surfaces gives rise to a localized state short below the conduction band (CB) edge while in bulk GaAs, the B impurity state is resonant with the CB. The analysis of BxGa1-xAs/GaAs quantum wells reveals a good crystal quality and shows that the incorporation of B atoms in GaAs can be controlled along the [001] growth direction at the atomic level. Surprisingly, the formation of the first and fourth nearest neighbor B pairs, which are oriented along the <110 > directions, is strongly suppressed at a B concentration of 1% while the third nearest neighbor B pairs are found more than twice as often than expected for a completely spatially random pattern.

JcDREB2, a Physic Nut AP2/ERF Gene, Alters Plant Growth and Salinity Stress Responses in Transgenic Rice.

PubMed

Tang, Yuehui; Liu, Kun; Zhang, Ju; Li, Xiaoli; Xu, Kedong; Zhang, Yi; Qi, Jing; Yu, Deshui; Wang, Jian; Li, Chengwei

2017-01-01

Transcription factors of the AP2/ERF family play important roles in plant growth, development, and responses to biotic and abiotic stresses. In this study, a physic nut AP2/ERF gene, JcDREB2 , was functionally characterized. Real-time PCR analysis revealed that JcDREB2 was expressed mainly in the leaf and could be induced by abscisic acid but suppressed by gibberellin (GA) and salt. Transient expression of a JcDREB2-YFP fusion protein in Arabidopsis protoplasts cells suggested that JcDREB2 is localized in the nucleus. Rice plants overexpressing JcDREB2 exhibited dwarf and GA-deficient phenotypes with shorter shoots and roots than those of wild-type plants. The dwarfism phenotype could be rescued by the application of exogenous GA 3 . The expression levels of GA biosynthetic genes including OsGA20ox1 , OsGA20ox2 , OsGA20ox4 , OsGA3ox2, OsCPS1 , OsKO2 , and OsKAO were significantly reduced in plants overexpressing JcDREB2 . Overexpression of JcDREB2 in rice increased sensitivity to salt stress. Increases in the expression levels of several salt-tolerance-related genes in response to salt stress were impaired in JcDREB2 -overexpressing plants. These results demonstrated not only that JcDREB2 influences GA metabolism, but also that it can participate in the regulation of the salt stress response in rice.

Dietary Fat, Fiber, and Carbohydrate Intake and Endogenous Hormone Levels in Premenopausal Women

PubMed Central

Cui, Xiaohui; Rosner, Bernard; Willett, Walter C; Hankinson, Susan E

2011-01-01

The authors conducted a cross-sectional study to investigate the associations of fat, fiber and carbohydrate intake with endogenous estrogen, androgen, and insulin-like growth factor (IGF) levels among 595 premenopausal women. Overall, no significant associations were found between dietary intake of these macronutrients and plasma sex steroid hormone levels. Dietary fat intake was inversely associated with IGF-I and IGF-binding protein 3 (IGFBP-3) levels. When substituting 5% of energy from total fat for the equivalent amount of energy from carbohydrate or protein intake, the plasma levels of IGF-I and IGFBP-3 were 2.8% (95% confidence interval [CI] 0.3, 5.3) and 1.6% (95% CI 0.4, 2.8) lower, respectively. Animal fat, saturated fat and monounsaturated fat intakes also were inversely associated with IGFBP-3 levels (P < 0.05). Carbohydrates were positively associated with plasma IGF-I level. When substituting 5% of energy from carbohydrates for the equivalent amount of energy from fat or protein intake, the plasma IGF-I level was 2.0% (95% CI 0.1, 3.9%) higher. No independent associations between fiber intake and hormone levels were observed. The results suggest that a low-fat/high-fiber or carbohydrate diet is not associated with endogenous levels of sex steroid hormones, but it may modestly increase IGF-I and IGFBP-3 levels among premenopausal women. PMID:21761370

A transient simulation approach to obtaining capacitance-voltage characteristics of GaN MOS capacitors with deep-level traps

NASA Astrophysics Data System (ADS)

Fukuda, Koichi; Asai, Hidehiro; Hattori, Junichi; Shimizu, Mitsuaki; Hashizume, Tamotsu

2018-04-01

In this study, GaN MOS capacitance-voltage device simulations considering various interface and bulk traps are performed in the transient mode. The simulations explain various features of capacitance-voltage curves, such as plateau, hysteresis, and frequency dispersions, which are commonly observed in measurements of GaN MOS capacitors and arise from complicated combinations of interface and bulk deep-level traps. The objective of the present study is to provide a good theoretical tool to understand the physics of various nonideal measured curves.

Deep levels in H-irradiated GaAs1-xNx (x < 0.01) grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Shafi, M.; Mari, R. H.; Khatab, A.; Henini, M.; Polimeni, A.; Capizzi, M.; Hopkinson, M.

2011-12-01

Dilute nitride GaAs1-xNx layers have been grown by molecular beam epitaxy with nitrogen concentration ranging from 0.2% to 0.8%. These samples have been studied before and after hydrogen irradiation by using standard deep level transient spectroscopy (DLTS) and high resolution Laplace DLTS techniques. The activation energy, capture cross section and density of the electron traps have been estimated and compared with results obtained in N-free as-grown and H-irradiated bulk GaAs.

Discriminating a deep gallium antisite defect from shallow acceptors in GaAs using supercell calculations

DOE PAGES

Schultz, Peter A.

2016-03-01

For the purposes of making reliable first-principles predictions of defect energies in semiconductors, it is crucial to distinguish between effective-mass-like defects, which cannot be treated accurately with existing supercell methods, and deep defects, for which density functional theory calculations can yield reliable predictions of defect energy levels. The gallium antisite defect GaAs is often associated with the 78/203 meV shallow double acceptor in Ga-rich gallium arsenide. Within a conceptual framework of level patterns, analyses of structure and spin stabilization can be used within a supercell approach to distinguish localized deep defect states from shallow acceptors such as B As. Thismore » systematic approach determines that the gallium antisite supercell results has signatures inconsistent with an effective mass state and cannot be the 78/203 shallow double acceptor. Lastly, the properties of the Ga antisite in GaAs are described, total energy calculations that explicitly map onto asymptotic discrete localized bulk states predict that the Ga antisite is a deep double acceptor and has at least one deep donor state.« less

High quality HfO{sub 2}/p-GaSb(001) metal-oxide-semiconductor capacitors with 0.8 nm equivalent oxide thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barth, Michael; Datta, Suman, E-mail: sdatta@engr.psu.edu; Bruce Rayner, G.

2014-12-01

We investigate in-situ cleaning of GaSb surfaces and its effect on the electrical performance of p-type GaSb metal-oxide-semiconductor capacitor (MOSCAP) using a remote hydrogen plasma. Ultrathin HfO{sub 2} films grown by atomic layer deposition were used as a high permittivity gate dielectric. Compared to conventional ex-situ chemical cleaning methods, the in-situ GaSb surface treatment resulted in a drastic improvement in the impedance characteristics of the MOSCAPs, directly evidencing a much lower interface trap density and enhanced Fermi level movement efficiency. We demonstrate that by using a combination of ex-situ and in-situ surface cleaning steps, aggressively scaled HfO{sub 2}/p-GaSb MOSCAP structuresmore » with a low equivalent oxide thickness of 0.8 nm and efficient gate modulation of the surface potential are achieved, allowing to push the Fermi level far away from the valence band edge high up into the band gap of GaSb.« less

Deep level transient spectroscopy signatures of majority traps in GaN p-n diodes grown by metal-organic vapor-phase epitaxy technique on GaN substrates

NASA Astrophysics Data System (ADS)

PŁaczek-Popko, E.; Trzmiel, J.; Zielony, E.; Grzanka, S.; Czernecki, R.; Suski, T.

2009-12-01

In this study, we present the results of investigation on p-n GaN diodes by means of deep level transient spectroscopy (DLTS) within the temperature range of 77-350 K. Si-doped GaN layers were grown by metal-organic vapor-phase epitaxy technique (MOVPE) on the free-standing GaN substrates. Subsequently Mg-doped GaN layers were grown. To perform DLTS measurements Ni/Au contacts to p-type material and Ti/Au contacts to n-type material were processed. DLTS signal spectra revealed the presence of two majority traps of activation energies obtained from Arrhenius plots equal to E1=0.22 eV and E2=0.65 eV. In present work we show that the trap E1 is linked with the extended defects whereas the trap E2 is the point defect related. Its capture cross section is thermally activated with energy barrier for capture equal to 0.2 eV.

Radiative recombination in GaN/InGaN heterojunction bipolar transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kao, Tsung-Ting; Lee, Yi-Che; Kim, Hee-Jin

2015-12-14

We report an electroluminescence (EL) study on npn GaN/InGaN heterojunction bipolar transistors (HBTs). Three radiative recombination paths are resolved in the HBTs, corresponding to the band-to-band transition (3.3 eV), conduction-band-to-acceptor-level transition (3.15 eV), and yellow luminescence (YL) with the emission peak at 2.2 eV. We further study possible light emission paths by operating the HBTs under different biasing conditions. The band-to-band and the conduction-band-to-acceptor-level transitions mostly arise from the intrinsic base region, while a defect-related YL band could likely originate from the quasi-neutral base region of a GaN/InGaN HBT. The I{sub B}-dependent EL intensities for these three recombination paths are discussed. The resultsmore » also show the radiative emission under the forward-active transistor mode operation is more effective than that using a diode-based emitter due to the enhanced excess electron concentration in the base region as increasing the collector current increases.« less

Transition-metal impurities in semiconductors and heterojunction band lineups

NASA Astrophysics Data System (ADS)

Langer, Jerzy M.; Delerue, C.; Lannoo, M.; Heinrich, Helmut

1988-10-01

The validity of a recent proposal that transition-metal impurity levels in semiconductors may serve as a reference in band alignment in semiconductor heterojunctions is positively verified by using the most recent data on band offsets in the following lattice-matched heterojunctions: Ga1-xAlxAs/GaAs, In1-xGaxAsyP1-y/InP, In1-xGaxP/GaAs, and Cd1-xHgxTe/CdTe. The alignment procedure is justified theoretically by showing that transition-metal energy levels are effectively pinned to the average dangling-bond energy level, which serves as the reference level for the heterojunction band alignment. Experimental and theoretical arguments showing that an increasingly popular notion on transition-metal energy-level pinning to the vacuum level is unjustified and must be abandoned in favor of the internal-reference rule proposed recently [J. M. Langer and H. Heinrich, Phys. Rev. Lett. 55, 1414 (1985)] are presented.

Protection from experimental asthma by an endogenous bronchodilator.

PubMed

Que, Loretta G; Liu, Limin; Yan, Yun; Whitehead, Gregory S; Gavett, Stephen H; Schwartz, David A; Stamler, Jonathan S

2005-06-10

Mechanisms that protect against asthma remain poorly understood. S-nitrosoglutathione (GSNO), an endogenous bronchodilator, is depleted from asthmatic airways, suggesting a protective role. We report that, following allergen challenge, wild-type mice exhibiting airway hyperresponsivity have increased airway levels of the enzyme GSNO reductase (GSNOR) and are depleted of lung S-nitrosothiols (SNOs). In contrast, mice with genetic deletion of GSNOR exhibit increases in lung SNOs and are protected from airway hyperresponsivity. Our results indicate that endogenous SNOs, governed by GSNOR, are critical regulators of airway responsivity and may provide new therapeutic approaches to asthma.

Accumulation and processing of a recombinant protein designed as a cleavable fusion to the endogenous Rubisco LSU protein in Chlamydomonas chloroplast

PubMed Central

Muto, Machiko; Henry, Ryan E; Mayfield, Stephen P

2009-01-01

Background Expression of recombinant proteins in green algal chloroplast holds substantial promise as a platform for the production of human therapeutic proteins. A number of proteins have been expressed in the chloroplast of Chlamydomonas reinhardtii, including complex mammalian proteins, but many of these proteins accumulate to significantly lower levels than do endogenous chloroplast proteins. We examined if recombinant protein accumulation could be enhanced by genetically fusing the recombinant reporter protein, luciferase, to the carboxy-terminal end of an abundant endogenous protein, the large subunit of ribulose bisphosphate carboxylase (Rubisco LSU). Additionally, as recombinant proteins fused to endogenous proteins are of little clinical or commercial value, we explored the possibility of engineering our recombinant protein to be cleavable from the endogenous protein in vivo. This strategy would obviate the need for further in vitro processing steps in order to produce the desired recombinant protein. To achieve this, a native protein-processing site from preferredoxin (preFd) was placed between the Rubisco LSU and luciferase coding regions in the fusion protein construct. Results The luciferase from the fusion protein accumulated to significantly higher levels than luciferase expressed alone. By eliminating the endogenous Rubisco large subunit gene (rbcL), we achieved a further increase in luciferase accumulation with respect to luciferase expression in the WT background. Importantly, near-wild type levels of functional Rubisco holoenzyme were generated following the proteolytic removal of the fused luciferase, while luciferase activity for the fusion protein was almost ~33 times greater than luciferase expressed alone. These data demonstrate the utility of using fusion proteins to enhance recombinant protein accumulation in algal chloroplasts, and also show that engineered proteolytic processing sites can be used to liberate the exogenous protein from the endogenous fusion partner, allowing for the purification of the intended mature protein. Conclusion These results demonstrate the utility of fusion proteins in algal chloroplast as a method to increase accumulation of recombinant proteins that are difficult to express. Since Rubisco is ubiquitous to land plants and green algae, this strategy may also be applied to higher plant transgenic expression systems. PMID:19323825

Identification of suitable reference genes for hepatic microRNA quantitation.

PubMed

Lamba, Vishal; Ghodke-Puranik, Yogita; Guan, Weihua; Lamba, Jatinder K

2014-03-07

MicroRNAs (miRNAs) are short (~22 nt) endogenous RNAs that play important roles in regulating expression of a wide variety of genes involved in different cellular processes. Alterations in microRNA expression patterns have been associated with a number of human diseases. Accurate quantitation of microRNA levels is important for their use as biomarkers and in determining their functions. Real time PCR is the gold standard and the most frequently used technique for miRNA quantitation. Real time PCR data analysis includes normalizing the amplification data to suitable endogenous control/s to ensure that microRNA quantitation is not affected by the variability that is potentially introduced at different experimental steps. U6 (RNU6A) and RNU6B are two commonly used endogenous controls in microRNA quantitation. The present study was designed to investigate inter-individual variability and gender differences in hepatic microRNA expression as well as to identify the best endogenous control/s that could be used for normalization of real-time expression data in liver samples. We used Taqman based real time PCR to quantitate hepatic expression levels of 22 microRNAs along with U6 and RNU6B in 50 human livers samples (25 M, 25 F). To identify the best endogenous controls for use in data analysis, we evaluated the amplified candidates for their stability (least variability) in expression using two commonly used software programs: Normfinder and GeNormplus, Both Normfinder and GeNormplus identified U6 to be among the least stable of all the candidates analyzed, and RNU6B was also not among the top genes in stability. mir-152 and mir-23b were identified to be the two most stable candidates by both Normfinder and GeNormplus in our analysis, and were used as endogenous controls for normalization of hepatic miRNA levels. Measurements of microRNA stability indicate that U6 and RNU6B are not suitable for use as endogenous controls for normalizing microRNA relative quantitation data in hepatic tissue, and their use can led to possibly erroneous conclusions.

Lumbar Osteophyte Avid on 68Ga-Prostate-Specific Membrane Antigen PET/CT.

PubMed

Jochumsen, Mads Ryø; Madsen, Michael Alle; Gammelgaard, Lise; Bouchelouche, Kirsten

2018-06-01

A 75-year-old man with recently diagnosed high-risk prostate cancer was referred for primary staging with Ga-prostate-specific membrane antigen (PSMA) PET/CT. The scan revealed intense Ga-PSMA uptake in a lumbar osteophyte on the right side of level L2/L3, whereas several other spinal osteophytes showed no Ga-PSMA uptake. MRI findings in the L3 vertebra was consistent with a benign Modic type 1 lesion, but MRI showed no signs of malignancy in the osteophyte with high Ga-PMSA uptake. This case presents an osteophyte as an addition to the list of potential benign pitfalls to be aware of when interpreting Ga-PSMA PET/CT.

Melatonin-induced CBF/DREB1s are essential for diurnal change of disease resistance and CCA1 expression in Arabidopsis.

PubMed

Shi, Haitao; Wei, Yunxie; He, Chaozu

2016-03-01

Melatonin (N-acetyl-5-methoxytryptamine) is an important regulator of circadian rhythms and immunity in animals. However, the diurnal changes of endogenous melatonin and melatonin-mediated diurnal change of downstream responses remain unclear in Arabidopsis. Using the publicly available microarray data, we found that the transcript levels of two melatonin synthesis genes (serotonin N-acetyltransferase (SNAT) and caffeate O-methyltransferase (COMT)) and endogenous melatonin level were regulated by diurnal cycles, with different magnitudes of change. Moreover, the transcripts of C-repeat-binding factors (CBFs)/Drought response element Binding 1 factors (DREB1s) were co-regulated by exogenous melatonin and diurnal changes, indicating the possible correlation among clock, endogenous melatonin level and AtCBFs expressions. Interestingly, diurnal change of plant immunity against Pst DC3000 and CIRCADIANCLOCK ASSOCIATED 1 (CCA1) expression were largely lost in AtCBFs knockdown line-amiR-1. Taken together, this study identifies the molecular pathway underlying the diurnal changes of immunity in Arabidopsis. Notably, the diurnal changes of endogenous melatonin may regulate corresponding changes of AtCBF/DREB1s expression and their underlying diurnal cycle of plant immunity and AtCCA1. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Nanoelectronics.

DTIC Science & Technology

1987-08-14

way to do this is to replace the continuous domain of the problem by a mesh or lattice of discrete points in phase space. The position coordinates x... lattice -matched GaAs / AlxGal.xAs heterojunction system. The central undoped GaAs quantum well is "sandwiched" between two Al 3Ga 7As barriers and n" GaAs...device defined as a "quantum coupled device" ( QCD ), which employs resonant tunneling between discrete electronic energy levels. Though difficult, creation

Enhanced piezoelectric output of NiO/nanoporous GaN by suppression of internal carrier screening

NASA Astrophysics Data System (ADS)

Waseem, Aadil; Jeong, Dae Kyung; Johar, Muhammad Ali; Kang, Jin-Ho; Ha, Jun-Seok; Key Lee, June; Ryu, Sang-Wan

2018-06-01

The efficiency of piezoelectric nanogenerators (PNGs) significantly depends on the free carrier concentration of semiconductors. In the presence of a mechanical stress, piezoelectric charges are generated at both ends of the PNG, which are rapidly screened by the free carriers. The screening effect rapidly decreases the piezoelectric output within fractions of a second. In this study, the piezoelectric outputs of bulk- and nanoporous GaN-based heterojunction PNGs are compared. GaN thin films were epitaxially grown on sapphire substrates using metal organic chemical vapor deposition. Nanoporous GaN was fabricated using electrochemical etching, depleted of free carriers owing to the surface Fermi-level pinning. A highly resistive NiO thin film was deposited on bulk- and nanoporous GaN using radio frequency magnetron sputter. The NiO/nanoporous GaN PNG (NPNG) under a periodic compressive stress of 4 MPa exhibited an output voltage and current of 0.32 V and 1.48 μA cm‑2, respectively. The output voltage and current of the NiO/thin film-GaN PNG (TPNG) were three and five times smaller than those of the NPNG, respectively. Therefore, the high-resistivity of NiO and nanoporous GaN depleted by the Fermi-level pinning are advantageous and provide a better piezoelectric performance of the NPNG, compared with that of the TPNG.

Consequences of adding gum Arabic as a cryoprotectant on motility and viability of frozen stallion semen.

PubMed

Ali, Mohamed; Musa, Musa M; Alfadul, Sulaiman; Al-Sobayel, K

2017-12-01

A trial was conducted to check effect of adding gum Arabic (GA) instead of egg yolk (EY) as a cryoprotectant for stallion sperm. Two experiments were designed; experiment I tested adding 3 levels of nonheated GA (i.e., 3, 6 and 9 g/100 mL diluents) in HF-20 extender. However, in experiment II the same levels were tested except that GA was heated at 80 °C for 60 min. HF-20 containing 10% of EY was used as control. In experiment I, sperm frozen in HF-20 containing nonheated GA exhibited lower percentages of motile sperm, progressively motile sperm and sperm with intact plasma membranes, vitality rate, and acrosome integrity after cooling or after deep freezing. Frozen semen in HF-20 containing 3-6% of preheated GA in experiment II maintained sperm motility at 46-50% and elevated progressive motility at 27%. The semen diluted in preheated GA (6%) and frozen exhibited a fertility rate of 40% (2/5). A similar fertility rate (40%) was found in the control semen (i.e. 10%) compared to those that were inseminated with frozen semen in preheated 3% GA (20%, 1/5). These results suggest that preheated GA could be used as an alternative cryoprotectant for cryopreserving stallion sperm. Copyright © 2017 Elsevier Inc. All rights reserved.

New approach to increasing rice lodging resistance and biomass yield through the use of high gibberellin producing varieties.

PubMed

Okuno, Ayako; Hirano, Ko; Asano, Kenji; Takase, Wakana; Masuda, Reiko; Morinaka, Yoichi; Ueguchi-Tanaka, Miyako; Kitano, Hidemi; Matsuoka, Makoto

2014-01-01

Traditional breeding for high-yielding rice has been dependent on the widespread use of fertilizers and the cultivation of gibberellin (GA)-deficient semi-dwarf varieties. The use of semi-dwarf plants facilitates high grain yield since these varieties possess high levels of lodging resistance, and thus could support the high grain weight. Although this approach has been successful in increasing grain yield, it is desirable to further improve grain production and also to breed for high biomass. In this study, we re-examined the effect of GA on rice lodging resistance and biomass yield using several GA-deficient mutants (e.g. having defects in the biosynthesis or perception of GA), and high-GA producing line or mutant. GA-deficient mutants displayed improved bending-type lodging resistance due to their short stature; however they showed reduced breaking-type lodging resistance and reduced total biomass. In plants producing high amounts of GA, the bending-type lodging resistance was inferior to the original cultivars. The breaking-type lodging resistance was improved due to increased lignin accumulation and/or larger culm diameters. Further, these lines had an increase in total biomass weight. These results show that the use of rice cultivars producing high levels of GA would be a novel approach to create higher lodging resistance and biomass.

Fabrication of gallium nitride nanowires by metal-assisted photochemical etching

NASA Astrophysics Data System (ADS)

Zhang, Miao-Rong; Jiang, Qing-Mei; Zhang, Shao-Hui; Wang, Zu-Gang; Hou, Fei; Pan, Ge-Bo

2017-11-01

Gallium nitride (GaN) nanowires (NWs) were fabricated by metal-assisted photochemical etching (MaPEtch). Gold nanoparticles (AuNPs) as metal catalyst were electrodeposited on the GaN substrate. SEM and HRTEM images show the surface of GaN NWs is smooth and clean without any impurity. SAED and FFT patterns demonstrate GaN NWs have single crystal structure, and the crystallographic orientation of GaN NWs is (0002) face. On the basis of the assumption of localized galvanic cells, combined with the energy levels and electrochemical potentials of reactants in this etching system, the generation, transfer and consumption of electron-hole pairs reveal the whole MaPEtch reaction process. Such easily fabricated GaN NWs have great potential for the assembly of GaN-based single-nanowire nanodevices.

Near-field microscopy of waveguide architectures of InGaN/GaN diode lasers

NASA Astrophysics Data System (ADS)

Friede, Sebastian; Tomm, Jens W.; Kühn, Sergei; Hoffmann, Veit; Wenzel, Hans; Weyers, Markus

2016-11-01

Waveguide (WG) architectures of 420 nm emitting InGaN/GaN diode lasers are analyzed by photoluminescence and photocurrent spectroscopy using a nearfield scanning optical microscope that scans along their front facets. The components of the ‘optical active cavity’, quantum wells, WGs, and cladding layers are individually inspected with a spatial resolution of ∼100 nm. Separate analysis of the p- and n-sections of the WG was achieved, and reveals defect levels in the p-part. Moreover, it is demonstrated that the homogeneity of the n-WG section directly affects the quantum wells that are grown on top of this layer. Substantially increased carrier capture efficiencies into InGaN/GaN-WGs compared to GaN-WGs are demonstrated.

68Ga-PSMA-PET/CT in Patients With Biochemical Prostate Cancer Recurrence and Negative 18F-Choline-PET/CT.

PubMed

Bluemel, Christina; Krebs, Markus; Polat, Bülent; Linke, Fränze; Eiber, Matthias; Samnick, Samuel; Lapa, Constantin; Lassmann, Michael; Riedmiller, Hubertus; Czernin, Johannes; Rubello, Domenico; Bley, Thorsten; Kropf, Saskia; Wester, Hans-Juergen; Buck, Andreas K; Herrmann, Ken

2016-07-01

Investigating the value of Ga-PSMA-PET/CT in biochemically recurring prostate cancer patients with negative F-choline-PET/CT. One hundred thirty-nine consecutive patients with biochemical recurrence after curative (surgery and/or radiotherapy) therapy were offered participation in this sequential clinical imaging approach. Patients first underwent an F-choline-PET/CT. If negative, an additional Ga-PSMA-PET/CT was offered. One hundred twenty-five of 139 eligible patients were included in the study; 32 patients underwent additional Ga-PSMA-PET/CT. Patients with equivocal findings (n = 5) on F-choline-PET/CT and those who declined the additional Ga-PSMA-PET/CT (n = 9) were excluded. Images were analyzed visually for the presence of suspicious lesions. Findings on PET/CT were correlated with PSA level, PSA doubling time (dt), and PSA velocity (vel). The overall detection rates were 85.6% (107/125) for the sequential imaging approach and 74.4% (93/125) for F-choline-PET/CT alone. Ga-PSMA-PET/CT detected sites of recurrence in 43.8% (14/32) of the choline-negative patients. Detection rates of the sequential imaging approach and F-choline-PET/CT alone increased with higher serum PSA levels and PSA vel. Subgroup analysis of Ga-PSMA-PET/CT in F-choline negative patients revealed detection rates of 28.6%, 45.5%, and 71.4% for PSA levels of 0.2 or greater to less than 1 ng/mL, 1 to 2 ng/mL, and greater than 2 ng/mL, respectively. The sequential imaging approach designed to limit Ga-PSMA imaging to patients with negative choline scans resulted in high detection rates. Ga-PSMA-PET/CT identified sites of recurrent disease in 43.8% of the patients with negative F-choline PET/CT scans.

68Ga-PSMA-PET/CT in Patients With Biochemical Prostate Cancer Recurrence and Negative 18F-Choline-PET/CT

PubMed Central

Bluemel, Christina; Krebs, Markus; Polat, Bülent; Linke, Fränze; Eiber, Matthias; Samnick, Samuel; Lapa, Constantin; Lassmann, Michael; Riedmiller, Hubertus; Czernin, Johannes; Rubello, Domenico; Bley, Thorsten; Kropf, Saskia; Wester, Hans-Juergen; Buck, Andreas K.; Herrmann, Ken

2016-01-01

Purpose Investigating the value of 68Ga-PSMA-PET/CT in biochemically recurring prostate cancer patients with negative 18F-choline-PET/CT. Patients and Methods One hundred thirty-nine consecutive patients with biochemical recurrence after curative (surgery and/or radiotherapy) therapy were offered participation in this sequential clinical imaging approach. Patients first underwent an 18F-choline-PET/CT. If negative, an additional 68Ga-PSMA-PET/CTwas offered. One hundred twenty-five of 139 eligible patients were included in the study; 32 patients underwent additional 68Ga-PSMA-PET/CT. Patients with equivocal findings (n = 5) on 18F-choline-PET/CT and those who declined the additional 68Ga-PSMA-PET/CT (n = 9) were excluded. Images were analyzed visually for the presence of suspicious lesions. Findings on PET/CT were correlated with PSA level, PSA doubling time (dt), and PSA velocity (vel). Results The overall detection rates were 85.6% (107/125) for the sequential imaging approach and 74.4% (93/125) for 18F-choline-PET/CT alone. 68Ga-PSMA-PET/CT detected sites of recurrence in 43.8% (14/32) of the choline-negative patients. Detection rates of the sequential imaging approach and 18F-choline-PET/CT alone increased with higher serum PSA levels and PSA vel. Subgroup analysis of 68Ga-PSMA-PET/CT in 18F-choline negative patients revealed detection rates of 28.6%, 45.5%, and 71.4% for PSA levels of 0.2 or greater to less than 1 ng/mL, 1 to 2 ng/mL, and greater than 2 ng/mL, respectively. Conclusions The sequential imaging approach designed to limit 68Ga-PSMA imaging to patients with negative choline scans resulted in high detection rates. 68Ga-PSMA-PET/CT identified sites of recurrent disease in 43.8% of the patients with negative 18F-choline PET/CT scans. PMID:26975008

Control over dark current densities and cutoff wavelengths of GaAs/AlGaAs QWIP grown by multi-wafer MBE reactor

NASA Astrophysics Data System (ADS)

Roodenko, K.; Choi, K. K.; Clark, K. P.; Fraser, E. D.; Vargason, K. W.; Kuo, J.-M.; Kao, Y.-C.; Pinsukanjana, P. R.

2016-09-01

Performance of quantum well infrared photodetector (QWIP) device parameters such as detector cutoff wavelength and the dark current density depend strongly on the quality and the control of the epitaxy material growth. In this work, we report on a methodology to precisely control these critical material parameters for long wavelength infrared (LWIR) GaAs/AlGaAs QWIP epi wafers grown by multi-wafer production Molecular beam epitaxy (MBE). Critical growth parameters such as quantum well (QW) thickness, AlGaAs composition and QW doping level are discussed.

AlGaInN laser diode technology and systems for defence and security applications

NASA Astrophysics Data System (ADS)

Najda, Stephen P.; Perlin, Piotr; Suski, Tadek; Marona, Lucja; Boćkowski, Mike; Leszczyński, Mike; Wisniewski, Przemek; Czernecki, Robert; Kucharski, Robert; Targowski, Grzegorz; Watson, Scott; Kelly, Antony E.

2015-05-01

The latest developments in AlGaInN laser diode technology are reviewed for defence and security applications such as underwater communications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Thus AlGaInN laser diode technology is a key enabler for the development of new disruptive system level applications in displays, telecom, defence and other industries.

Association of LIPC -250G>A polymorphism and several environmental factors with serum lipid levels in the Guangxi Bai Ku Yao and Han populations

PubMed Central

2010-01-01

Background The association between -250G>A polymorphism in the promoter region of the hepatic lipase gene (LIPC) and plasma high-density lipoprotein cholesterol (HDL-C) concentration is contradictory in diverse ethnics. Bai Ku Yao is an isolated subgroup of the Yao minority in China. This study was designed to detect the association of LIPC -250G>A (rs2070895) polymorphism and several environmental factors with serum lipid levels in the Guangxi Bai Ku Yao and Han populations. Methods A total of 778 subjects of Bai Ku Yao and 648 participants of Han Chinese aged 15-80 were randomly selected from our previous stratified randomized cluster samples. Genotyping of the LIPC -250G>A was performed by polymerse chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing. Results The levels of serum total cholesterol (TC), HDL-C, low-density lipoprotein cholesterol (LDL-C) and apolipoprotein (Apo) AI were lower in Bai Ku Yao than in Han (P < 0.01 for all). The frequencies of GG, GA and AA genotypes were 50.0%, 43.3% and 6.7% in Bai Ku Yao, and 35.7%, 50.6% and 13.7% in Han (P < 0.01); respectively. The frequencies of G and A alleles were 71.7% and 28.3% in Bai Ku Yao, and 61.0% and 39.0% in Han (P < 0.01). The levels of HDL-C and the ratio of ApoAI to ApoB in Bai Ku Yao were lower in GG genotype than in GA or AA genotype (P < 0.05-0.01). The levels of TC, HDL-C, LDL-C and ApoB in Han were lower in GG genotype than in GA or AA genotype (P < 0.05-0.01). The levels of HDL-C and the ratio of ApoAI to ApoB in Bai Ku Yao, and the levels of HDL-C, LDL-C and ApoB in Han were correlated with genotype and/or allele (P < 0.05 for all). Serum lipid parameters were also correlated with age, sex, alcohol consumption, cigarette smoking, blood pressure, body weight, and body mass index in both ethnic groups. Conclusions The differences in the serum lipid profiles between the two ethnic groups might partly result from different genotypic frequency of LIPC -250G>A or different LIPC-enviromental interactions. PMID:20222961

Engineering alfalfa to accumulate useful caffeic acid derivatives and characterization of hydroxycinnamoyl-CoA transferases from legumes

USDA-ARS?s Scientific Manuscript database

Some forages crops, such as red clover, accumulate high levels of caffeic acid derivatives. Oxidation of these o-diphenols to quinones by endogenous polyphenol oxidases (PPOs) and the subsequent reactions of these quinones (probably with endogenous plant proteases) result in a significant reduction ...

Live Imaging of Endogenous PSD-95 Using ENABLED: A Conditional Strategy to Fluorescently Label Endogenous Proteins

PubMed Central

Fortin, Dale A.; Tillo, Shane E.; Yang, Guang; Rah, Jong-Cheol; Melander, Joshua B.; Bai, Suxia; Soler-Cedeño, Omar; Qin, Maozhen; Zemelman, Boris V.; Guo, Caiying

2014-01-01

Stoichiometric labeling of endogenous synaptic proteins for high-contrast live-cell imaging in brain tissue remains challenging. Here, we describe a conditional mouse genetic strategy termed endogenous labeling via exon duplication (ENABLED), which can be used to fluorescently label endogenous proteins with near ideal properties in all neurons, a sparse subset of neurons, or specific neuronal subtypes. We used this method to label the postsynaptic density protein PSD-95 with mVenus without overexpression side effects. We demonstrated that mVenus-tagged PSD-95 is functionally equivalent to wild-type PSD-95 and that PSD-95 is present in nearly all dendritic spines in CA1 neurons. Within spines, while PSD-95 exhibited low mobility under basal conditions, its levels could be regulated by chronic changes in neuronal activity. Notably, labeled PSD-95 also allowed us to visualize and unambiguously examine otherwise-unidentifiable excitatory shaft synapses in aspiny neurons, such as parvalbumin-positive interneurons and dopaminergic neurons. Our results demonstrate that the ENABLED strategy provides a valuable new approach to study the dynamics of endogenous synaptic proteins in vivo. PMID:25505322

Onsite Calibration of a Precision IPRT Based on Gallium and Gallium-Based Small-Size Eutectic Points

NASA Astrophysics Data System (ADS)

Sun, Jianping; Hao, Xiaopeng; Zeng, Fanchao; Zhang, Lin; Fang, Xinyun

2017-04-01

Onsite thermometer calibration with temperature scale transfer technology based on fixed points can effectively improve the level of industrial temperature measurement and calibration. The present work performs an onsite calibration of a precision industrial platinum resistance thermometer near room temperature. The calibration is based on a series of small-size eutectic points, including Ga-In (15.7°C), Ga-Sn (20.5°C), Ga-Zn (25.2°C), and a Ga fixed point (29.7°C), developed in a portable multi-point automatic realization apparatus. The temperature plateaus of the Ga-In, Ga-Sn, and Ga-Zn eutectic points and the Ga fixed point last for longer than 2 h, and their reproducibility was better than 5 mK. The device is suitable for calibrating non-detachable temperature sensors in advanced environmental laboratories and industrial fields.

The structural and optical properties of GaSb/InGaAs type-II quantum dots grown on InP (100) substrate

PubMed Central

2012-01-01

We have investigated the structural and optical properties of type-II GaSb/InGaAs quantum dots [QDs] grown on InP (100) substrate by molecular beam epitaxy. Rectangular-shaped GaSb QDs were well developed and no nanodash-like structures which could be easily found in the InAs/InP QD system were formed. Low-temperature photoluminescence spectra show there are two peaks centered at 0.75eV and 0.76ev. The low-energy peak blueshifted with increasing excitation power is identified as the indirect transition from the InGaAs conduction band to the GaSb hole level (type-II), and the high-energy peak is identified as the direct transition (type-I) of GaSb QDs. This material system shows a promising application on quantum-dot infrared detectors and quantum-dot field-effect transistor. PMID:22277096

Determining the band alignment of TbAs:GaAs and TbAs:In 0.53Ga 0.47As

DOE PAGES

Bomberger, Cory C.; Vanderhoef, Laura R.; Rahman, Abdur; ...

2015-09-10

Here, we propose and systematically justify a band structure for TbAs nanoparticles in GaAs and In 0.53Ga 0.47As host matrices. Moreover, fluence-dependent optical-pump terahertz-probe measurements suggest the TbAs nanoparticles have a band gap and provide information on the carrier dynamics, which are determined by the band alignment. Spectrophotometry measurements provide the energy of optical transitions in the nanocomposite systems and reveal a large blue shift in the absorption energy when the host matrix is changed from In 0.53Ga 0.47As to GaAs. Finally, Hall data provides the approximate Fermi level in each system. From this data, we deduce that the TbAs:GaAsmore » system forms a type I (straddling) heterojunction and the TbAs:In 0.53Ga 0.47As system forms a type II (staggered) heterojunction.« less

Origin and enhancement of the 1.3 μm luminescence from GaAs treated by ion-implantation and flash lamp annealing

NASA Astrophysics Data System (ADS)

Gao, Kun; Prucnal, S.; Skorupa, W.; Helm, M.; Zhou, Shengqiang

2013-09-01

GaAs and GaAs based materials have outstanding optoelectronic properties and are widely used as light emitting media in devices. Many approaches have been applied to GaAs to generate luminescence at 0.88, 1.30, and 1.55 μm which are transmission windows of optical fibers. In this paper, we present the photoluminescence at 1.30 μm from deep level defects in GaAs treated by ion-implantation and flash lamp annealing (FLA). Such emission, which exhibits superior temperature stability, can be obtained from FLA treated virgin GaAs as well as doped GaAs. Indium-doping in GaAs can greatly enhance the luminescence. By photoluminescence, Raman measurements, and positron annihilation spectroscopy, we conclude that the origin of the 1.30 μm emission is from transitions between the VAs-donor and X-acceptor pairs.

Development, Validation, and Interlaboratory Evaluation of a Quantitative Multiplexing Method To Assess Levels of Ten Endogenous Allergens in Soybean Seed and Its Application to Field Trials Spanning Three Growing Seasons.

PubMed

Hill, Ryan C; Oman, Trent J; Wang, Xiujuan; Shan, Guomin; Schafer, Barry; Herman, Rod A; Tobias, Rowel; Shippar, Jeff; Malayappan, Bhaskar; Sheng, Li; Xu, Austin; Bradshaw, Jason

2017-07-12

As part of the regulatory approval process in Europe, comparison of endogenous soybean allergen levels between genetically engineered (GE) and non-GE plants has been requested. A quantitative multiplex analytical method using tandem mass spectrometry was developed and validated to measure 10 potential soybean allergens from soybean seed. The analytical method was implemented at six laboratories to demonstrate the robustness of the method and further applied to three soybean field studies across multiple growing seasons (including 21 non-GE soybean varieties) to assess the natural variation of allergen levels. The results show environmental factors contribute more than genetic factors to the large variation in allergen abundance (2- to 50-fold between environmental replicates) as well as a large contribution of Gly m 5 and Gly m 6 to the total allergen profile, calling into question the scientific rational for measurement of endogenous allergen levels between GE and non-GE varieties in the safety assessment.

Electrical conductivity of In2O3 and Ga2O3 after low temperature ion irradiation; implications for instrinsic defect formation and charge neutrality level.

PubMed

Vines, L; Bhoodoo, C; von Wenckstern, H; Grundmann, M

2017-12-13

The evolution of sheet resistance of n-type In 2 O 3 and Ga 2 O 3 exposed to bombardment with MeV 12 C and 28 Si ions at 35 K is studied in situ. While the sheet resistance of Ga 2 O 3 increased by more than eight orders of magnitude as a result of ion irradiation, In 2 O 3 showed a more complex defect evolution and became more conductive when irradiated at the highest doses. Heating up to room temperature reduced the sheet resistivity somewhat, but Ga 2 O 3 remained highly resistive, while In 2 O 3 showed a lower resistance than as deposited samples. Thermal admittance spectroscopy and deep level transient spectroscopy did not reveal new defect levels for irradiation up to [Formula: see text] cm -2 . A model where larger defect complexes preferentially produce donor like defects in In 2 O 3 is proposed, and may reveal a microscopic view of a charge neutrality level within the conduction band, as previously proposed.

Electrical conductivity of In2O3 and Ga2O3 after low temperature ion irradiation; implications for instrinsic defect formation and charge neutrality level

NASA Astrophysics Data System (ADS)

Vines, L.; Bhoodoo, C.; von Wenckstern, H.; Grundmann, M.

2018-01-01

The evolution of sheet resistance of n-type In2O3 and Ga2O3 exposed to bombardment with MeV 12C and 28Si ions at 35 K is studied in situ. While the sheet resistance of Ga2O3 increased by more than eight orders of magnitude as a result of ion irradiation, In2O3 showed a more complex defect evolution and became more conductive when irradiated at the highest doses. Heating up to room temperature reduced the sheet resistivity somewhat, but Ga2O3 remained highly resistive, while In2O3 showed a lower resistance than as deposited samples. Thermal admittance spectroscopy and deep level transient spectroscopy did not reveal new defect levels for irradiation up to 2 × 1012 cm-2. A model where larger defect complexes preferentially produce donor like defects in In2O3 is proposed, and may reveal a microscopic view of a charge neutrality level within the conduction band, as previously proposed.

Simple intrinsic defects in GaP and InP

NASA Astrophysics Data System (ADS)

Schultz, Peter A.

2012-02-01

To faithfully simulate evolution of defect chemistry and electrical response in irradiated semiconductor devices requires accurate defect reaction energies and energy levels. In III-Vs, good data is scarce, theory hampered by band gap and supercell problems. I apply density functional theory (DFT) to intrinsic defects in GaP and InP, predicting stable charge states, ground state configurations, defect energy levels, and identifying mobile species. The SeqQuest calculations incorporate rigorous charge boundary conditions removing supercell artifacts, demonstrated converged to the infinite limit. Computed defect levels are not limited by a band gap problem, despite Kohn-Sham gaps much smaller than the experimental gap. As in GaAs, [P.A. Schultz and O.A. von Lilienfeld, Modeling Simul. Mater. Sci. Eng. 17, 084007 (2009)], defects in GaP and InP exhibit great complexity---multitudes of charge states, bistabilities, and negative U systems---but show similarities to each other (and to GaAs). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

New Insights on β-Thalassemia in the Palestinian Population of Gaza: High Frequency and Milder Phenotype Among Homozygous IVS-I-1 (HBB: c.92+1G>A) Patients with High Levels of Hb F.

PubMed

Ghoti, Hussam; Fibach, Eitan; Rachmilewitz, Eliezer A; Jeadi, Hisham; Filon, Dvora

2017-03-01

β-Thalassemia (β-thal) is a very common disease in the Palestinian population of the Gaza Strip. We studied their mutation frequency and clinical features. Thirteen different mutations were identified. The most common mutation was IVS-I-1 (G>A) (HBB: c.92+1G>A), which was prevalent in 31.5% of the thalassemia alleles studied. The IVS-I-110 (G>A) (HBB: c.93-21G>A) mutation was found in 25.0% of the alleles. Homozygotes for the IVS-I-1 mutation had higher mean hemoglobin (Hb) levels, required less blood transfusions, and lower transferrin saturation than the homozygotes for the IVS-I-110 mutation. This milder phenotype was, most likely, the result of the persistent production of Hb F; it was 9-fold higher in absolute terms (g/dL) and 7.7-fold higher in relative terms (percentage of total Hb). About half of our IVS-I-1 patients carried the XmnI polymorphism, which is known to be associated with elevated Hb F levels.

68Ga-PSMA PET/CT in the evaluation of bone metastases in prostate cancer.

PubMed

Sachpekidis, Christos; Bäumer, P; Kopka, K; Hadaschik, B A; Hohenfellner, M; Kopp-Schneider, A; Haberkorn, U; Dimitrakopoulou-Strauss, A

2018-06-01

The aims of this retrospective analysis were to compare 68 Ga-PSMA PET findings and low-dose CT findings (120 kV, 30 mA), and to obtain semiquantitative and quantitative 68 Ga-PSMA PET data in patients with prostate cancer (PC) bone metastases. In total, 152 PET/CT scans from 140 patients were evaluated. Of these patients, 30 had previously untreated primary PC, and 110 had biochemical relapse after treatment of primary PC. All patients underwent dynamic PET/CT scanning of the pelvis and lower abdomen as well as whole-body PET/CT with 68 Ga-PSMA-11. The PET/CT scans were analysed qualitatively (visually), semiquantitatively (SUV), and quantitatively based on a two-tissue compartment model and a noncompartmental approach leading to the extraction of the fractal dimension. Differences were considered significant for p values <0.05. In total, 168 68 Ga-PSMA-positive and 113 CT-positive skeletal lesions were detected in 37 patients (8 with primary PC, 29 with biochemical recurrence). Of these 168 lesions, 103 were both 68 Ga-PSMA PET-positive and CT-positive, 65 were only 68 Ga-PSMA-positive, and 10 were only CT-positive. The Yang test showed that there were significantly more 68 Ga-PSMA PET-positive lesions than CT-positive lesions. Association analysis showed that PSA plasma levels were significantly correlated with several 68 Ga-PSMA-11-associated parameters in bone metastases, including the degree of tracer uptake (SUV average and SUV max ), its transport rate from plasma to the interstitial/intracellular compartment (K 1 ), its rate of binding to the PSMA receptor and its internalization (k 3 ), its influx rate (K i ), and its distribution heterogeneity. 68 Ga-PSMA PET/CT is a useful diagnostic tool in the detection of bone metastases in PC. 68 Ga-PSMA PET visualizes more bone metastases than low-dose CT. PSA plasma levels are significantly correlated with several 68 Ga-PSMA PET parameters.

The toxic effect of gallic acid on biochemical factors, viability and proliferation of rat bone marrow mesenchymal stem cells was compensated by boric acid.

PubMed

Abnosi, Mohammad Hussein; Yari, Somayeh

2018-07-01

Gallic acid (GA) and boron are found in many plants. Our previous studies showed 6 ng/ml boric acid (BA) had positive effect on biochemistry of rat bone marrow mesenchymal stem cells (MSCs) and their osteogenic differentiation. Therefore, we investigate the effect of different doses of GA alone and in the presence of BA on MSCs. the viability of MSCs was assayed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and trypan blue at 12, 24 and 36 h in presence of different concentration of GA. Then 30 and 120 μM of GA as well as 6 ng/ml of BA in 36 h were selected for further study. The proliferation, Morphology, sodium and potassium level, concentration of calcium, activity of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) as well as malondialdehyde (MDA) concentration, total antioxidant capacity (FRAP) and activity of superoxide dismutase (SOD) and catalase (CAT) were estimated. Results showed GA alone reduced viability, proliferation, nuclear diameter and cytoplasm area. In addition, GA showed anaerobic metabolic shift but no change in MDA and scavenging enzymes. Both concentration of GA caused elevation of FRAP, whereas only at 120 μM increased the sodium-potassium and reduced calcium. The co-treatment of GA and BA improves the viability, proliferation and morphology of the cells. In addition, co-treatment compensated the metabolic shift caused by GA and could balance the potassium level and FRAP as it was raised by GA. Although GA content of tea is harmful to the cells but simultaneous consumption of fruits and vegetables as a rich source of boron might compensate the damaging effect of GA. Copyright © 2018 Elsevier GmbH. All rights reserved.

Effect of uniaxial stress on electroluminescence, valence band modification, optical gain, and polarization modes in tensile strained p-AlGaAs/GaAsP/n-AlGaAs laser diode structures: Numerical calculations and experimental results

NASA Astrophysics Data System (ADS)

Bogdanov, E. V.; Minina, N. Ya.; Tomm, J. W.; Kissel, H.

2012-11-01

The effects of uniaxial compression in [110] direction on energy-band structures, heavy and light hole mixing, optical matrix elements, and gain in laser diodes with "light hole up" configuration of valence band levels in GaAsP quantum wells with different widths and phosphorus contents are numerically calculated. The development of light and heavy hole mixing caused by symmetry lowering and converging behavior of light and heavy hole levels in such quantum wells under uniaxial compression is displayed. The light or heavy hole nature of each level is established for all considered values of uniaxial stress. The results of optical gain calculations for TM and TE polarization modes show that uniaxial compression leads to a significant increase of the TE mode and a minor decrease of the TM mode. Electroluminescence experiments were performed under uniaxial compression up to 5 kbar at 77 K on a model laser diode structure (p-AlxGa1-xAs/GaAs1-yPy/n-AlxGa1-xAs) with y = 0.16 and a quantum well width of 14 nm. They reveal a maximum blue shift of 27 meV of the electroluminescence spectra that is well described by the calculated change of the optical gap and the increase of the intensity being referred to a TE mode enhancement. Numerical calculations and electroluminescence data indicate that uniaxial compression may be used for a moderate wavelength and TM/TE intensity ratio tuning.

Preparation of p-type GaN-doped SnO2 thin films by e-beam evaporation and their applications in p-n junction

NASA Astrophysics Data System (ADS)

Lv, Shuliang; Zhou, Yawei; Xu, Wenwu; Mao, Wenfeng; Wang, Lingtao; Liu, Yong; He, Chunqing

2018-01-01

Various transparent GaN-doped SnO2 thin films were deposited on glass substrates by e-beam evaporation using GaN:SnO2 targets of different GaN weight ratios. It is interesting to find that carrier polarity of the thin films was converted from n-type to p-type with increasing GaN ratio higher than 15 wt.%. The n-p transition in GaN-doped SnO2 thin films was explained for the formation of GaSn and NO with increasing GaN doping level in the films, which was identified by Hall measurement and XPS analysis. A transparent thin film p-n junction was successfully fabricated by depositing p-type GaN:SnO2 thin film on SnO2 thin film, and a low leakage current (6.2 × 10-5 A at -4 V) and a low turn-on voltage of 1.69 V were obtained for the p-n junction.

High quality lamella preparation of gallium nitride compound semiconductor using Triple Beam™ system

NASA Astrophysics Data System (ADS)

Sato, T.; Nakano, K.; Matsumoto, H.; Torikawa, S.; Nakatani, I.; Kiyohara, M.; Isshiki, T.

2017-09-01

Gallium nitride (GaN) compound semiconductors have been known to be very sensitive to Ga focused ion beam (FIB) processing. Due to the nature of GaN based materials it is often difficult to produce damage-free lamellae, therefore applying the Triple Beam™ system which incorporates an enhanced method for amorphous removal is presented to make a high quality lamella. The damage or distortion layer thickness of GaN single crystal prepared with 30 kV Ga FIB and 1 kV Ga FIB were about 17 nm and 1.5 nm respectively. The crystallinity at the uppermost surface remained unaffected when the condition of 1 kV Ar ion milling with the Triple Beam™ system was used. The technique of combining traditional Ga FIB processing with an enhanced method for amorphous layer removal by low energy Ar ion milling allows us to analyse the InGaN/GaN interface using aberration corrected scanning transmission electron microscopy at atomic resolution levels.

68Ga-PSMA-11 PET/CT Mapping of Prostate Cancer Biochemical Recurrence After Radical Prostatectomy in 270 Patients with a PSA Level of Less Than 1.0 ng/mL: Impact on Salvage Radiotherapy Planning.

PubMed

Calais, Jeremie; Czernin, Johannes; Cao, Minsong; Kishan, Amar U; Hegde, John V; Shaverdian, Narek; Sandler, Kiri; Chu, Fang-I; King, Chris R; Steinberg, Michael L; Rauscher, Isabel; Schmidt-Hegemann, Nina-Sophie; Poeppel, Thorsten; Hetkamp, Philipp; Ceci, Francesco; Herrmann, Ken; Fendler, Wolfgang P; Eiber, Matthias; Nickols, Nicholas G

2018-02-01

Target volume delineations for prostate cancer (PCa) salvage radiotherapy (SRT) after radical prostatectomy are usually drawn in the absence of visibly recurrent disease. 68 Ga-labeled prostate-specific membrane antigen (PSMA-11) PET/CT detects recurrent PCa with sensitivity superior to standard-of-care imaging at serum prostate-specific antigen (PSA) values low enough to affect target volume delineations for routine SRT. Our objective was to map the recurrence pattern of PCa early biochemical recurrence (BCR) after radical prostatectomy with 68 Ga-PSMA-11 PET/CT in patients with serum PSA levels of less than 1 ng/mL, determine how often consensus clinical target volumes (CTVs) based on the Radiation Therapy Oncology Group (RTOG) guidelines cover 68 Ga-PSMA-11 PET/CT-defined disease, and assess the potential impact of 68 Ga-PSMA-11 PET/CT on SRT. Methods: This was a post hoc analysis of an intention-to-treat population of 270 patients who underwent 68 Ga-PSMA-11 PET/CT at 4 institutions for BCR after prostatectomy without prior radiotherapy at a PSA level of less than 1 ng/mL. RTOG consensus CTVs that included both the prostate bed and the pelvic lymph nodes were contoured on the CT dataset of the PET/CT image by a radiation oncologist masked to the PET component. 68 Ga-PSMA-11 PET/CT images were analyzed by a nuclear medicine physician. 68 Ga-PSMA-11-positive lesions not covered by planning volumes based on the consensus CTVs were considered to have a potential major impact on treatment planning. Results: The median PSA level at the time of 68 Ga-PSMA-11 PET/CT was 0.48 ng/mL (range, 0.03-1 ng/mL). One hundred thirty-two of 270 patients (49%) had a positive 68 Ga-PSMA-11 PET/CT result. Fifty-two of 270 (19%) had at least one PSMA-11-positive lesion not covered by the consensus CTVs. Thirty-three of 270 (12%) had extrapelvic PSMA-11-positive lesions, and 19 of 270 (7%) had PSMA-11-positive lesions within the pelvis but not covered by the consensus CTVs. The 2 most common 68 Ga-PSMA-11-positive lesion locations outside the consensus CTVs were bone (23/52, 44%) and perirectal lymph nodes (16/52, 31%). Conclusion: Post hoc analysis of 68 Ga-PSMA-11 PET/CT implied a major impact on SRT planning in 52 of 270 patients (19%) with PCa early BCR (PSA < 1.0 ng/mL). This finding justifies a randomized imaging trial of SRT with or without 68 Ga-PSMA-11 PET/CT investigating its potential benefit on clinical outcome. © 2018 by the Society of Nuclear Medicine and Molecular Imaging.

Defect studies in one MeV electron irradiated GaAs and in Al/sub x Ga/sub l-x As P-N junction solar cells

NASA Technical Reports Server (NTRS)

Li, S. S.; Wang, W. L.; Loo, R. Y.; Rahilly, W. P.

1984-01-01

Deep level transient spectroscopy reveals that the main electron traps for one-MeV electron irradiated GaAs cells are E9c)-0.31, E(c)-0.90 eV, and the main hole trap is due to the level. Electron trap density was found to vary from 3/tens-trillion ccm for 2/one quadrillion cm 3/3.7 quadrillion cm for 21 sextillion cm electron fluence for electron fluence; a similar result was also obtained for the hole trap density. As for the grown-in defects in the Al(x)Ga(1-x)As p-n junciton cells, only two electron traps with energies of E(c)-0.20 and E(c)-0.34 eV were observed in samples with x = 0.17, and none was found for x 0.05. Auger analysis on the Al(x)Ga(1-x) As window layer of the GaAs solar cell showed a large amount of oxygen and carbon contaminants near the surface of the AlGaAs epilayer. Thermal annealing experiment performed at 250 C for up to 100 min. showed a reduction in the density of both electron traps.

Doping dependent crystal structures and optoelectronic properties of n-type CdSe:Ga nanowries.

PubMed

Hu, Zhizhong; Zhang, Xiujuan; Xie, Chao; Wu, Chunyan; Zhang, Xiaozhen; Bian, Liang; Wu, Yiming; Wang, Li; Zhang, Yuping; Jie, Jiansheng

2011-11-01

Although CdSe nanostructures possess excellent electrical and optical properties, efforts to make nano-optoelectronic devices from CdSe nanostructures have been hampered by the lack of efficient methods to rationally control their structural and electrical characteristics. Here, we report CdSe nanowires (NWs) with doping dependent crystal structures and optoelectronic properties by using gallium (Ga) as the efficient n-type dopant via a simple thermal co-evaporation method. The phase change of CdSe NWs from wurtzite to zinc blende with increased doping level is observed. Systematical measurements on the transport properties of the CdSe:Ga NWs reveal that the NW conductivity could be tuned in a wide range of near nine orders of magnitude by adjusting the Ga doping level and a high electron concentration up to 4.5 × 10(19) cm(-3) is obtained. Moreover, high-performance top-gate field-effect transistors are constructed based on the individual CdSe:Ga NWs by using high-κ HfO(2) as the gate dielectric. The great potential of the CdSe:Ga NWs as high-sensitive photodetectors and nanoscale light emitters is also exploited, revealing the promising applications of the CdSe:Ga NWs in new-generation nano-optoelectronics.

Growth and graviresponsiveness of primary roots of Zea mays seedlings deficient in abscisic acid and gibberellic acid

NASA Technical Reports Server (NTRS)

Moore, R.; Dickey, K.

1985-01-01

The objective of this research was to determine if gibberellic acid (GA) and/or abscisic acid (ABA) are necessary for graviresponsiveness by primary roots of Zea mays. To accomplish this objective we measured the growth and graviresponsiveness of primary roots of seedlings in which the synthesis of ABA and GA was inhibited collectively and individually by genetic and chemical means. Roots of seedlings treated with Fluridone (an inhibitor of ABA biosynthesis) and Ancymidol (an inhibitor of GA biosynthesis) were characterized by slower growth rates but not significantly different gravicultures as compared to untreated controls. Gravicurvatures of primary roots of d-5 mutants (having undetectable levels of GA) and vp-9 mutants (having undectable levels of ABA) were not significantly different from those of wild-type seedlings. Roots of seedlings in which the biosynthesis of ABA and GA was collectively inhibited were characterized by gravicurvatures not significantly different for those of controls. These results (1) indicate that drastic reductions in the amount of ABA and GA in Z. mays seedlings do not significantly alter root graviresponsiveness, (2) suggest that neither ABA nor GA is necessary for root gravicurvature, and (3) indicate that root gravicurvature is not necessarily proportional to root elongation.

TNF-α -308G/A gene polymorphism in bullous pemphigoid and alopecia areata.

PubMed

Moravvej, Hamideh; Tabatabaei-Panah, Pardis-Sadat; Ebrahimi, Elaheh; Esmaeili, Nafiseh; Ghaderian, Sayyed Mohammad Hossein; Ludwig, Ralf J; Akbarzadeh, Reza

2018-05-11

TNF-α -308G/A polymorphism has been investigated in few studies for an association with susceptibility to bullous pemphigoid (BP) and alopecia areata (AA). Yet, these findings had so far not been independently replicated, and no data on a possible association of TNFα -308G/A polymorphism with these diseases in Iranian population were available. In the present study, a possible effect of TNF-α -308G/A variation on susceptibility to BP or AA disease was evaluated. Genomic DNA was extracted from the blood of the patients with BP and AA as well as control subjects which genotyped for the TNF-α -308 G/A polymorphism. TNF-α gene expression levels were analyzed by real-time RT-PCR. No association was observed between the TNF-α -308 G/A variation and susceptibility to BP or AA diseases in our Iranian cohort. In contrast to AA patients, expression of TNF-α gene was significantly higher in BP patients compared to control group. TNF-α gene was found to be similarly expressed in mutant and wild-type genotypes. TNF-α -308G/A polymorphism is not associated with the risk to develop of BP and AA in our Iranian cohort. Furthermore, this polymorphism is not contributed to altering the levels of gene expression in both diseases.

Sink limitation induces the expression of multiple soybean vegetative lipoxygenase mRNAs while the endogenous jasmonic acid level remains low.

PubMed Central

Bunker, T W; Koetje, D S; Stephenson, L C; Creelman, R A; Mullet, J E; Grimes, H D

1995-01-01

The response of individual members of the lipoxygenase multigene family in soybeans to sink deprivation was analyzed. RNase protection assays indicated that a novel vegetative lipoxygenase gene, vlxC, and three other vegetative lipoxygenase mRNAs accumulated in mature leaves in response to a variety of sink limitations. These data suggest that several members of the lipoxygenase multigene family are involved in assimilate partitioning. The possible involvement of jasmonic acid as a signaling molecule regulating assimilate partitioning into the vegetative storage proteins and lipoxygenases was directly assessed by determining the endogenous level of jasmonic acid in leaves from plants with their pods removed. There was no rise in the level of endogenous jasmonic acid coincident with the strong increase in both vlxC and vegetative storage protein VspB transcripts in response to sink limitation. Thus, expression of the vegetative lipoxygenases and vegetative storage proteins is not regulated by jasmonic acid in sink-limited leaves. PMID:7549487

Sink limitation induces the expression of multiple soybean vegetative lipoxygenase mRNAs while the endogenous jasmonic acid level remains low.

PubMed

Bunker, T W; Koetje, D S; Stephenson, L C; Creelman, R A; Mullet, J E; Grimes, H D

1995-08-01

The response of individual members of the lipoxygenase multigene family in soybeans to sink deprivation was analyzed. RNase protection assays indicated that a novel vegetative lipoxygenase gene, vlxC, and three other vegetative lipoxygenase mRNAs accumulated in mature leaves in response to a variety of sink limitations. These data suggest that several members of the lipoxygenase multigene family are involved in assimilate partitioning. The possible involvement of jasmonic acid as a signaling molecule regulating assimilate partitioning into the vegetative storage proteins and lipoxygenases was directly assessed by determining the endogenous level of jasmonic acid in leaves from plants with their pods removed. There was no rise in the level of endogenous jasmonic acid coincident with the strong increase in both vlxC and vegetative storage protein VspB transcripts in response to sink limitation. Thus, expression of the vegetative lipoxygenases and vegetative storage proteins is not regulated by jasmonic acid in sink-limited leaves.

Detecting Fermi-level shifts by Auger electron spectroscopy in Si and GaAs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debehets, J.; Homm, P.; Menghini, M.

In this study, changes in surface Fermi-level of Si and GaAs, caused by doping and cleaning, are investigated by Auger electron spectroscopy. Based on the Auger voltage contrast, we compared the Auger transition peak energy but with higher accuracy by using a more accurate analyzer and an improved peak position determination method. For silicon, a peak shift as large as 0.46 eV was detected when comparing a cleaned p-type and n-type wafer, which corresponds rather well with the theoretical difference in Fermi-levels. If no cleaning was applied, the peak position did not differ significantly for both wafer types, indicating Fermi-levelmore » pinning in the band gap. For GaAs, peak shifts were detected after cleaning with HF and (NH 4) 2S-solutions in an inert atmosphere (N 2-gas). Although the (NH 4) 2S-cleaning in N 2 is very efficient in removing the oxygen from the surface, the observed Ga- and As-peak shifts are smaller than those obtained after the HF-cleaning. It is shown that the magnitude of the shift is related to the surface composition. After Si-deposition on the (NH 4) 2S-cleaned surface, the Fermi-level shifts back to a similar position as observed for an as-received wafer, indicating that this combination is not successful in unpinning the Fermi-level of GaAs.« less

Detecting Fermi-level shifts by Auger electron spectroscopy in Si and GaAs

DOE PAGES

Debehets, J.; Homm, P.; Menghini, M.; ...

2018-01-12

In this study, changes in surface Fermi-level of Si and GaAs, caused by doping and cleaning, are investigated by Auger electron spectroscopy. Based on the Auger voltage contrast, we compared the Auger transition peak energy but with higher accuracy by using a more accurate analyzer and an improved peak position determination method. For silicon, a peak shift as large as 0.46 eV was detected when comparing a cleaned p-type and n-type wafer, which corresponds rather well with the theoretical difference in Fermi-levels. If no cleaning was applied, the peak position did not differ significantly for both wafer types, indicating Fermi-levelmore » pinning in the band gap. For GaAs, peak shifts were detected after cleaning with HF and (NH 4) 2S-solutions in an inert atmosphere (N 2-gas). Although the (NH 4) 2S-cleaning in N 2 is very efficient in removing the oxygen from the surface, the observed Ga- and As-peak shifts are smaller than those obtained after the HF-cleaning. It is shown that the magnitude of the shift is related to the surface composition. After Si-deposition on the (NH 4) 2S-cleaned surface, the Fermi-level shifts back to a similar position as observed for an as-received wafer, indicating that this combination is not successful in unpinning the Fermi-level of GaAs.« less

Modeling and optimization of a double-well double-barrier GaN/AlGaN/GaN/AlGaN resonant tunneling diode

NASA Astrophysics Data System (ADS)

Liu, Yang; Gao, Bo; Gong, Min; Shi, Ruiying

2017-06-01

The influence of a GaN layer as a sub-quantum well for an AlGaN/GaN/AlGaN double barrier resonant tunneling diode (RTD) on device performance has been investigated by means of numerical simulation. The introduction of the GaN layer as the sub-quantum well turns the dominant transport mechanism of RTD from the 3D-2D model to the 2D-2D model and increases the energy difference between tunneling energy levels. It can also lower the effective height of the emitter barrier. Consequently, the peak current and peak-to-valley current difference of RTD have been increased. The optimal GaN sub-quantum well parameters are found through analyzing the electrical performance, energy band, and transmission coefficient of RTD with different widths and depths of the GaN sub-quantum well. The most pronounced electrical parameters, a peak current density of 5800 KA/cm2, a peak-to-valley current difference of 1.466 A, and a peak-to-valley current ratio of 6.35, could be achieved by designing RTD with the active region structure of GaN/Al0.2Ga0.8 N/GaN/Al0.2Ga0.8 N (3 nm/1.5 nm/1.5 nm/1.5 nm).

Lattice damage and compositional changes in Xe ion irradiated In{sub x}Ga{sub 1-x}N (x = 0.32−1.0) single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Limin, E-mail: zhanglm@lzu.edu.cn; Peng, Jinxin; Ai, Wensi

2016-06-28

Lattice disorder and compositional changes in In{sub x}Ga{sub 1-x}N (x = 0.32, 0.47, 0.7, 0.8, and 1.0) films on GaN/Al{sub 2}O{sub 3} substrates, induced by room-temperature irradiation of 5 MeV Xe ions, have been investigated using both Rutherford backscattering spectrometry under ion-channeling conditions and time-of-flight secondary ion mass spectrometry. The results show that for a fluence of 3 × 10{sup 13 }cm{sup −2}, the relative level of lattice disorder in In{sub x}Ga{sub 1-x}N increases monotonically from 59% to 90% with increasing indium concentration x from 0.32 to 0.7; a further increase in x up to 1.0 leads to little increase in the disorder level. In contrastmore » to Ga-rich In{sub x}Ga{sub 1-x}N (x = 0.32 and 0.47), significant volume swelling of up to ∼25% accompanied with oxidation in In-rich In{sub x}Ga{sub 1-x}N (x = 0.7, 0.8, and 1.0) is observed. In addition, irradiation-induced atomic mixing occurs at the interface of In-rich In{sub x}Ga{sub 1-x}N and GaN. The results from this study indicate an extreme susceptibility of the high In-content In{sub x}Ga{sub 1-x}N to heavy-ion irradiation, and suggest that cautions must be exercised in applying ion-implantation techniques to these materials at room temperature. Further studies of the irradiation behavior at elevated temperatures are warranted.« less

The anti-cancer agent guttiferone-A permeabilizes mitochondrial membrane: Ensuing energetic and oxidative stress implications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pardo-Andreu, Gilberto L., E-mail: gilbertopardo@infomed.sld.cu; Departamento de Fisica e Quimica, Faculdade de Ciencias Farmaceuticas de Ribeirao Preto, Universidade de Sao Paulo, Av. Cafe s/n, 14040-903 Ribeirao Preto, SP; Nunez-Figueredo, Yanier

Guttiferone-A (GA) is a natural occurring polyisoprenylated benzophenone with cytotoxic action in vitro and anti-tumor action in rodent models. We addressed a potential involvement of mitochondria in GA toxicity (1-25 {mu}M) toward cancer cells by employing both hepatic carcinoma (HepG2) cells and succinate-energized mitochondria, isolated from rat liver. In HepG2 cells GA decreased viability, dissipated mitochondrial membrane potential, depleted ATP and increased reactive oxygen species (ROS) levels. In isolated rat-liver mitochondria GA promoted membrane fluidity increase, cyclosporine A/EGTA-insensitive membrane permeabilization, uncoupling (membrane potential dissipation/state 4 respiration rate increase), Ca{sup 2+} efflux, ATP depletion, NAD(P)H depletion/oxidation and ROS levels increase. Allmore » effects in cells, except mitochondrial membrane potential dissipation, as well as NADPH depletion/oxidation and permeabilization in isolated mitochondria, were partly prevented by the a NAD(P)H regenerating substrate isocitrate. The results suggest the following sequence of events: 1) GA interaction with mitochondrial membrane promoting its permeabilization; 2) mitochondrial membrane potential dissipation; 3) NAD(P)H oxidation/depletion due to inability of membrane potential-sensitive NADP{sup +} transhydrogenase of sustaining its reduced state; 4) ROS accumulation inside mitochondria and cells; 5) additional mitochondrial membrane permeabilization due to ROS; and 6) ATP depletion. These GA actions are potentially implicated in the well-documented anti-cancer property of GA/structure related compounds. - Graphical abstract: Guttiferone-A permeabilizes mitochondrial membrane and induces cancer cell death Display Omitted Highlights: > We addressed the involvement of mitochondria in guttiferone (GA) toxicity toward cancer cells. > GA promoted membrane permeabilization, membrane potential dissipation, NAD(P)H depletion, ROS accumulation and ATP depletion. > These actions could be implicated in the well-documented anti-cancer property of GA/structure related compounds.« less

68Ga-PSMA PET/CT in Patients with Rising Prostatic-Specific Antigen After Definitive Treatment of Prostate Cancer: Detection Efficacy and Diagnostic accuracy.

PubMed

Hamed, Maged Abdel Galil; Basha, Mohammad Abd Alkhalik; Ahmed, Hussien; Obaya, Ahmed Ali; Afifi, Amira Hamed Mohamed; Abdelbary, Eman H

2018-06-20

68 Ga-prostate-specific membrane antigen-11 ( 68 Ga-PSMA-11) is a recently developed positron emission tomography (PET) tracer that can detect prostate cancer (PC) relapses and metastases with high contrast resolution. The aim of this study was to assess the detection efficacy and diagnostic accuracy of 68 Ga-PSMA PET/CT image in patients with rising prostatic-specific antigen (PSA) after treatment of PC. The present prospective study included 188 patients who exhibited rising of PSA level on a routine follow-up examination after definitive treatment of PC. All patients underwent a 68 Ga-PSMA PET/CT examination. For each patient, we determined the disease stage, the Gleason score, and the maximum standardized uptake value of the local recurrence and extraprostatic metastases. The detection efficacy and diagnostic accuracy of 68 Ga-PSMA PET/CT were established by histopathology and clinical and imaging follow-up as the reference standards. 68 Ga-PSMA PET/CT detected tumour relapse in 165 patients (35 patients had local recurrence, 106 patients had extraprostatic metastases, and 24 patients had combined lesions). The sensitivity, specificity, and accuracy values of 68 Ga-PSMA PET/CT examination in the detection of PC recurrence were 98.8%, 100%, and 98.8%, respectively. 68 Ga-PSMA PET/CT revealed an overall detection rate of 87.8% (165/188) in patients with rising PSA (median of 2.2 ng/mL, and range of 0.01-70 ng/mL). 68 Ga-PSMA PET/CT is a valuable tool for the detection of PC local recurrence or extraprostatic metastases following rising PSA levels after primary definitive therapy and should be incorporated during routine work-up. Copyright © 2018. Published by Elsevier Inc.

High Temperature Heterojunction Bipolar Transistors

DTIC Science & Technology

1994-04-15

Furthermore, p-type doping has only recently been announced in GaN,󈧒 and p-type conductivity had to be induced by irradiating Mg-doped GaN with a low ...confinement of the electron gas by a potential barrier should not be a problem even for low In concentrations. Although InN is not lattice matched to GaN...epitaxy.3 The films were grown by the reaction of Ga vapor with ECR-activated nitrogen . This study found that at low microwave power levels

Advances in single mode and high power AlGaInN laser diode technology for systems applications

NASA Astrophysics Data System (ADS)

Najda, Stephen P.; Perlin, Piotr; Suski, Tadek; Marona, Lujca; Boćkowski, Michal; Leszczyński, Mike; Wisniewski, Przemek; Czernecki, Robert; Kucharski, Robert; Targowski, Grzegorz; Smalc-Koziorowska, Julita; Stanczyk, Szymon; Watson, Scott; Kelly, Antony E.

2015-03-01

The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well. Thus AlGaInN laser diode technology is a key enabler for the development of new disruptive system level applications in displays, telecom, defence and other industries.

The usefulness of cytogenetic parameters, level of p53 protein and endogenous glutathione as intermediate end-points in raw betel-nut genotoxicity.

PubMed

Kumpawat, K; Chatterjee, A

2003-07-01

Betel-nut (BN) chewing related oral mucosal lesions are potential hazards to a large population worldwide. Genotoxicity of betel alkaloids, polyphenol and tannin fractions have been reported. It has been shown earlier that BN ingredients altered the level of endogenous glutathione (GSH) which could modulate the host susceptibility to the action of other chemical carcinogens. The north-east Indian variety of BN, locally known as 'kwai', is raw, wet and consumed unprocessed with betel-leaf and slaked lime and contains higher alkaloids, polyphenol and tannins as compared to the dried one. Therefore, the purpose of this study was to investigate the extent of DNA damage, pattern of cell kinetics, the level of p53-protein and endogenous GSH in kwai chewers in the tribal population of Meghalaya state in the northeastern region of India with an aim to see whether these end-points could serve as biomarkers of genetic damage of relevance for genotoxic/carcinogenic process. The present data show higher DNA damage, delay in cell kinetics, p53 expression and lower GSH-level in heavy chewers (HC) than nonchewers (NC). The influence of bleomycin (BLM) on chromatid break induction in G2-phase of peripheral blood lymphocytes in NC and HC has been analysed to determine individual susceptibility to carcinogenic assaults. HC showed higher induction of chromatid breaks than NC. Risk assessment in this study suggests an interaction between carcinogen exposure and mutagen sensitivity measures, risk estimates being higher in those individuals who both consume kwai and express sensitivity to free radical oxygen damage in vitro. From this study it seems that besides cytogenetical parameters, the level of endogenous GSH and the level of p53 protein could act as effective biomarkers for kwai chewers.