16 results on '"Yangqiao Zheng"'
Search Results
2. Supplementary Figure from Tumor-Naïve Multimodal Profiling of Circulating Tumor DNA in Head and Neck Squamous Cell Carcinoma
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Scott V. Bratman, Daniel D. De Carvalho, Michael M. Hoffman, David P. Goldstein, John R. de Almeida, Lillian L. Siu, Anna Spreafico, Ilan Weinreb, John N. Waldron, Geoffrey Liu, Fei-Fei Liu, Wei Xu, Sareh Keshavarzi, Shao Hui Huang, Shu Yi Shen, Yangqiao Zheng, Zhen Zhao, Jinfeng Zou, and Justin M. Burgener
- Abstract
Supplementary Figure from Tumor-Naïve Multimodal Profiling of Circulating Tumor DNA in Head and Neck Squamous Cell Carcinoma
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- 2023
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3. Supplementary Data from HPV Sequencing Facilitates Ultrasensitive Detection of HPV Circulating Tumor DNA
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Scott V. Bratman, Trevor J. Pugh, Lillian L. Siu, Ariana Rostami, Ting Ting Wang, Yangqiao Zheng, Zhen Zhao, Jinfeng Zou, Kathy Han, and Eric Leung
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Supplementary Data from HPV Sequencing Facilitates Ultrasensitive Detection of HPV Circulating Tumor DNA
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- 2023
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4. Supplementary Figure from HPV Sequencing Facilitates Ultrasensitive Detection of HPV Circulating Tumor DNA
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Scott V. Bratman, Trevor J. Pugh, Lillian L. Siu, Ariana Rostami, Ting Ting Wang, Yangqiao Zheng, Zhen Zhao, Jinfeng Zou, Kathy Han, and Eric Leung
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Supplementary Figure from HPV Sequencing Facilitates Ultrasensitive Detection of HPV Circulating Tumor DNA
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- 2023
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5. Supplementary Data from Tumor-Naïve Multimodal Profiling of Circulating Tumor DNA in Head and Neck Squamous Cell Carcinoma
- Author
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Scott V. Bratman, Daniel D. De Carvalho, Michael M. Hoffman, David P. Goldstein, John R. de Almeida, Lillian L. Siu, Anna Spreafico, Ilan Weinreb, John N. Waldron, Geoffrey Liu, Fei-Fei Liu, Wei Xu, Sareh Keshavarzi, Shao Hui Huang, Shu Yi Shen, Yangqiao Zheng, Zhen Zhao, Jinfeng Zou, and Justin M. Burgener
- Abstract
Supplementary Data from Tumor-Naïve Multimodal Profiling of Circulating Tumor DNA in Head and Neck Squamous Cell Carcinoma
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- 2023
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- View/download PDF
6. Data from Tumor-Naïve Multimodal Profiling of Circulating Tumor DNA in Head and Neck Squamous Cell Carcinoma
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Scott V. Bratman, Daniel D. De Carvalho, Michael M. Hoffman, David P. Goldstein, John R. de Almeida, Lillian L. Siu, Anna Spreafico, Ilan Weinreb, John N. Waldron, Geoffrey Liu, Fei-Fei Liu, Wei Xu, Sareh Keshavarzi, Shao Hui Huang, Shu Yi Shen, Yangqiao Zheng, Zhen Zhao, Jinfeng Zou, and Justin M. Burgener
- Abstract
Purpose:Circulating tumor DNA (ctDNA) enables personalized treatment strategies in oncology by providing a noninvasive source of clinical biomarkers. In patients with low ctDNA abundance, tumor-naïve methods are needed to facilitate clinical implementation. Here, using locoregionally confined head and neck squamous cell carcinoma (HNSCC) as an example, we demonstrate tumor-naïve detection of ctDNA by simultaneous profiling of mutations and methylation.Experimental Design:We conducted CAncer Personalized Profiling by deep Sequencing (CAPP-seq) and cell-free Methylated DNA ImmunoPrecipitation and high-throughput sequencing (cfMeDIP-seq) for detection of ctDNA-derived somatic mutations and aberrant methylation, respectively. We analyzed 77 plasma samples from 30 patients with stage I–IVA human papillomavirus–negative HNSCC as well as plasma samples from 20 risk-matched healthy controls. In addition, we analyzed leukocytes from patients and controls.Results:CAPP-seq identified mutations in 20 of 30 patients at frequencies similar to that of The Tumor Genome Atlas (TCGA). Differential methylation analysis of cfMeDIP-seq profiles identified 941 ctDNA-derived hypermethylated regions enriched for CpG islands and HNSCC-specific methylation patterns. Both methods demonstrated an association between ctDNA abundance and shorter fragment lengths. In addition, mutation- and methylation-based ctDNA abundance was highly correlated (r > 0.85). Patients with detectable pretreatment ctDNA by both methods demonstrated significantly worse overall survival (HR = 7.5; P = 0.025) independent of clinical stage, with lack of ctDNA clearance post-treatment strongly correlating with recurrence. We further leveraged cfMeDIP-seq profiles to validate a prognostic signature identified from TCGA samples.Conclusions:Tumor-naïve detection of ctDNA by multimodal profiling may facilitate biomarker discovery and clinical use in low ctDNA abundance applications.
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- 2023
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7. Data from HPV Sequencing Facilitates Ultrasensitive Detection of HPV Circulating Tumor DNA
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Scott V. Bratman, Trevor J. Pugh, Lillian L. Siu, Ariana Rostami, Ting Ting Wang, Yangqiao Zheng, Zhen Zhao, Jinfeng Zou, Kathy Han, and Eric Leung
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Purpose:Human papillomavirus (HPV) DNA offers a convenient circulating tumor DNA (ctDNA) marker for HPV-associated malignancies, but current methods, such as digital PCR (dPCR), provide insufficient accuracy for clinical applications in patients with low disease burden. We asked whether a next-generation sequencing approach, HPV sequencing (HPV-seq), could provide quantitative and qualitative assessment of HPV ctDNA in low disease burden settings.Experimental Design:We conducted preclinical technical validation studies on HPV-seq and applied it retrospectively to a prospective multicenter cohort of patients with locally advanced cervix cancer (NCT02388698) and a cohort of patients with oropharynx cancer. HPV-seq results were compared with dPCR. The primary outcome was progression-free survival (PFS) according to end-of-treatment HPV ctDNA detectability.Results:HPV-seq achieved reproducible detection of HPV DNA at levels less than 0.6 copies in cell line data. HPV-seq and dPCR results for patients were highly correlated (R2 = 0.95, P = 1.9 × 10–29) with HPV-seq detecting ctDNA at levels down to 0.03 copies/mL plasma in dPCR-negative posttreatment samples. Detectable HPV ctDNA at end-of-treatment was associated with inferior PFS with 100% sensitivity and 67% specificity for recurrence. Accurate HPV genotyping was successful from 100% of pretreatment samples. HPV ctDNA fragment sizes were consistently shorter than non–cancer-derived cell-free DNA (cfDNA) fragments, and stereotyped cfDNA fragmentomic patterns were observed across HPV genomes.Conclusions:HPV-seq is a quantitative method for ctDNA detection that outperforms dPCR and reveals qualitative information about ctDNA. Our findings in this proof-of-principle study could have implications for treatment monitoring of disease burden in HPV-related cancers. Future prospective studies are needed to confirm that patients with undetectable HPV ctDNA following chemoradiotherapy have exceptionally high cure rates.
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- 2023
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8. Cell-Free DNA Kinetics in a Pre-Clinical Model of Head and Neck Cancer
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Scott V. Bratman, Cheng S. Jin, Harley H.L. Chan, Nidal Muhanna, Marco A. Di Grappa, Yangqiao Zheng, Tahsin Khan, and Jonathan C. Irish
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0301 basic medicine ,Male ,Future studies ,Tomography Scanners, X-Ray Computed ,Kinetics ,lcsh:Medicine ,Sensitivity and Specificity ,Article ,Circulating Tumor DNA ,03 medical and health sciences ,0302 clinical medicine ,Medicine ,Animals ,Recurrent tumour ,lcsh:Science ,Lymph node ,Multidisciplinary ,Total plasma ,business.industry ,Squamous Cell Carcinoma of Head and Neck ,Head and neck cancer ,lcsh:R ,medicine.disease ,Head and neck squamous-cell carcinoma ,Tumor Burden ,030104 developmental biology ,medicine.anatomical_structure ,Cell-free fetal DNA ,Head and Neck Neoplasms ,030220 oncology & carcinogenesis ,Cancer research ,lcsh:Q ,Rabbits ,business ,Cell-Free Nucleic Acids ,Neoplasm Transplantation - Abstract
In cancer patients, circulating tumour-derived DNA (ctDNA) levels imperfectly reflect disease burden apparent on medical imaging. Further evaluation of ctDNA levels over time is needed to better understand the correlation with tumour growth and therapeutic response. We describe ctDNA kinetics within an orthotopic, immunocompetent preclinical rabbit model of local-regionally advanced head and neck squamous cell carcinoma (HNSCC). Monitoring primary tumour and metastatic lymph node volume by computed tomography (CT), we observed a correlation between ctDNA levels and tumour burden. We found that ctDNA detection could precede evidence of tumour on CT. Sensitivity and specificity of ctDNA detection in this model was 90.2% (95% C.I.: 76.9–97.3%) and 85.7% (95% C.I.: 67.3–96.0%), respectively. Rapid tumour growth followed by auto-necrosis and tumour volume contraction produced a spike in ctDNA levels, suggesting that viable tumour cells may be required for sustained ctDNA release. Following surgical resection, both ctDNA and total plasma DNA were correlated with recurrent tumour volume. Our results reveal the complex kinetic behaviour of ctDNA and total plasma DNA upon tumour growth or surgery. This pre-clinical model could be useful for future studies focused on elucidating mechanisms of ctDNA release into the circulation from primary and metastatic sites.
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- 2017
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9. Abstract A45: HPV sequencing facilitates ultrasensitive detection of HPV circulating tumor DNA
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Eric Leung, Yangqiao Zheng, Jinfeng Zou, Ting Ting Wang, Scott V. Bratman, Zhen Zhao, Lillian L. Siu, Kathy Han, and Trevor J. Pugh
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Oncology ,Cancer Research ,medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,Cancer ,Disease ,medicine.disease ,Minimal residual disease ,female genital diseases and pregnancy complications ,medicine.anatomical_structure ,Internal medicine ,Medicine ,business ,Prospective cohort study ,Adjuvant ,Cervix ,Chemoradiotherapy ,Cohort study - Abstract
Background: Human papillomavirus (HPV)-associated cancers often present with locoregionally confined disease and are treated with curative intent. An emerging treatment paradigm includes radical therapy (i.e., chemoradiotherapy or surgery) followed by adjuvant treatment. Accurate detection of minimal residual disease (MRD) following radical therapy could enable personalized use of adjuvant treatment. The HPV genome offers a convenient circulating tumor (ct)DNA marker for HPV-associated cancers, but current methods such as digital (d)PCR provide insufficient accuracy for accurate MRD detection and for other clinical applications in patients with low disease burden. We asked whether a next-generation sequencing approach (HPV-seq) could provide quantitative and qualitative assessment of HPV ctDNA in low-disease-burden settings. Methods: We conducted preclinical technical validation studies on HPV-seq using cervix cancer cell lines. We then applied HPV-seq retrospectively to a prospective multicenter cohort study of locally advanced cervix cancer patients accrued from 2015 to 2016 (NCT02388698). Patients were treated with radical chemoradiotherapy with blood obtained at baseline, end of treatment, and 3 months post-treatment. Median follow-up was 27.5 months. In 38 plasma samples from 17 patients, HPV-seq results were compared with dPCR. The primary outcome was progression-free survival according to end-of-treatment HPV ctDNA detectability. Results: HPV-seq achieved reproducible detection of HPV DNA at levels Conclusions: HPV-seq is a quantitative method for ctDNA detection that outperforms dPCR. HPV-seq also reveals qualitative information about ctDNA fragments such as HPV genotype and ctDNA fragment length distribution. Our findings will have implications for MRD detection in HPV-related cancers. Future prospective studies are needed to confirm that patients with undetectable HPV ctDNA following chemoradiotherapy have exceptionally high cure rates. Citation Format: Eric Leung, Kathy Han, Jinfeng Zou, Zhen Zhao, Yangqiao Zheng, Ting Ting Wang, Lillian L. Siu, Trevor J. Pugh, Scott V. Bratman. HPV sequencing facilitates ultrasensitive detection of HPV circulating tumor DNA [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr A45.
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- 2020
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10. High Interpatient Variability in Molecular MRD Response to Consolidation Chemotherapy in Acute Myeloid Leukemia
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Mark D. Minden, Steven M. Chan, Dawn Maze, Hassan Sibai, Tracy Murphy, Scott V. Bratman, Philip C. Zuzarte, Zhen Zhao, Caroline J McNamara, Paul M. Krzyzanowski, Karen W.L. Yee, Jinfeng Zou, Andre C. Schuh, Ting Ting Wang, Carolina Bocanegra, Yangqiao Zheng, Aaron D. Schimmer, Roman M Shapiro, Lawrence E. Heisler, Tracy Stockley, Vikas Gupta, and Trevor J. Pugh
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Oncology ,medicine.medical_specialty ,MRD Response ,business.industry ,Immunology ,Disease progression ,Myeloid leukemia ,Consolidation Chemotherapy ,Cell Biology ,Hematology ,Biochemistry ,Chemotherapy regimen ,Log-rank test ,Internal medicine ,Mann–Whitney U test ,Medicine ,business ,Whole blood - Abstract
Introduction: Although induction chemotherapy results in a complete remission (CR) in ~70% of newly diagnosed AML patients, post-remission therapies are needed to eliminate minimal residual disease (MRD) and prevent relapse. Consolidation chemotherapy, either as definitive therapy or bridge to bone marrow transplantation (BMT), is currently the most common form of post-remission therapy. Yet, our understanding of its impact on MRD remains limited. In this study, we investigated the effects of consolidation chemotherapy on molecular MRD (mMRD) burden using ultra-deep next generation sequencing (NGS) and correlated treatment response with disease characteristics and survival outcomes in AML patients. Patients and Methods: 91 newly diagnosed AML patients who achieved CR following standard induction chemotherapy were evaluated. Targeted conventional NGS using a 54-gene panel was performed on whole blood (PB) or bone marrow samples collected at diagnosis. PB samples were collected during remission at two consecutive time points (T1 and T2), before and after 1 (n=79) or 2 (n=12) cycles of consolidation chemotherapy, for each patient. To detect mMRD, we used a custom 37-gene hybrid-capture panel and error-corrected NGS based on the duplex sequencing approach with a variant allele frequency (VAF) detection limit of ~1x10-4. For 10 patients, we also performed duplex sequencing analysis on their relapsed samples. Results: NGS of the diagnostic samples identified a total of 298 putative oncogenic mutations in 92% (n=84) of the 91 patients. Ninety percent of these mutations (n=267) were trackable by the custom hybrid-capture panel. Duplex sequencing detected persistence of 56% (n=149) of the trackable mutations in T1 samples; 34% (n=50) of which were clonal hematopoiesis-associated DTA mutations (those involving DNMT3A, TET2, or ASXL1), and the remaining 66% (n=99) were non-DTA mutations. Analysis of T2 samples showed that consolidation chemotherapy reduced the VAF of non-DTA mutations by a median of 73% and cleared 27% (n=27) of them at T2. In contrast, the burden of DTA mutations increased by 0.5% (P < 0.0001 by Mann-Whitney test), and only 2% (n=1) of the mutations was cleared (P = 0.0001 by Fisher's exact test). These findings are consistent with prior studies demonstrating that non-DTA mutations are more reliable markers of leukemic burden than DTA mutations. To study the impact of consolidation chemotherapy at the level of individual patients, the mean VAF of all persistent non-DTA mutations was calculated for each sample and used as a composite measure of mMRD burden (henceforth referred to as "cmMRD"). Analysis of the 10 patients with relapsed samples showed that cmMRD levels tracked well with achievement of remission and disease progression (Fig. 1). In the subset of patients with persistent non-DTA mutations at T1 (n=61), consolidation chemotherapy decreased cmMRD levels by a median of 36% at T2. However, we observed high interpatient variability (Fig. 2); 36% (n=22) of the patients experienced an increase in cmMRD burden after consolidation chemotherapy, and 36% (n=22) had less than a 1 log reduction. Only 28% (n=17) of the patients achieved a log reduction of greater than 1. The likelihood and magnitude of cmMRD response were significantly associated with cytogenetic risk (P = 0.026 by 3x3 Chi-square test; Fig. 3). The proportion of patients with favorable, intermediate, and poor-risk cytogenetics who experienced cmMRD expansion was 17%, 27%, and 71%, respectively. Consistent with these findings, a suboptimal response (defined as cmMRD ratio [T2/T1] > 0.4) was associated with inferior overall survival (HR = 3.29, P = 0.007 by log-rank test; Fig. 4). Conclusions: Our analysis showed that mMRD response to consolidation chemotherapy was highly variable among patients. Although consolidation chemotherapy was effective in deepening the remission for a subset of patients, it failed to lower MRD levels for a substantial proportion of patients, especially those with poor risk cytogenetics. These findings challenge the practice of using consolidation chemotherapy to achieve a deeper remission prior to BMT for high-risk patients and indicate that the opposite outcome may occur instead. NGS-based monitoring of mMRD can potentially be used to distinguish between patients who can remain on consolidation chemotherapy as definitive therapy and those who require a switch in post-remission therapy. Disclosures Gupta: Sierra Oncology: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Honoraria, Research Funding. Maze:Pfizer Inc: Consultancy; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. McNamara:Novartis Pharmaceutical Canada Inc.: Consultancy. Minden:Trillium Therapetuics: Other: licensing agreement. Schimmer:Medivir Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Consultancy; Novartis Pharmaceuticals: Consultancy; Otsuka Pharmaceuticals: Consultancy. Schuh:Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees; Agios: Honoraria; Astellas: Honoraria, Membership on an entity's Board of Directors or advisory committees; Teva Canada Innovation: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Yee:Novartis, Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas, Celgene, Otsuka, Shire, Takeda: Membership on an entity's Board of Directors or advisory committees; Agensys, Astex, Hoffman La Roche, MedImmune, Merck, Millenium, Roche/Genentech: Research Funding. Bratman:SVB: Other: is co-inventor of a patent relating to circulating tumor DNA detection technology, which has been licensed to Roche Molecular Diagnostics.. Chan:Agios: Honoraria; AbbVie Pharmaceuticals: Research Funding; Celgene: Honoraria, Research Funding.
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- 2019
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11. Combined effects of light and nitrate supplies on the growth, photosynthesis and ultraviolet-absorbing compounds in marine macroalgaGracilaria lemaneiformis(Rhodophyta), with special reference to the effects of solar ultraviolet radiation
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Yangqiao Zheng
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Photoinhibition ,integumentary system ,fungi ,Plant Science ,Aquatic Science ,Photosynthetic efficiency ,Biology ,Photosynthesis ,Agricultural and Biological Sciences (miscellaneous) ,Thallus ,chemistry.chemical_compound ,Nutrient ,Nitrate ,chemistry ,Photosynthetically active radiation ,Botany ,Respiration rate - Abstract
Summary It is well known that light and nutrients are essential to plants; however, there are few investigations in which these have been studied in combination on macroalgae, especially when solar ultraviolet radiation (UVR) is concerned. We cultured the red alga Gracilaria lemaneiformis (Bory) at different nitrate concentrations and light levels with or without UVR for 24 days. The results showed that nitrate supply markedly enhanced the growth and photosynthesis, increased the absorptivity of UV-absorbing compounds (UVACs), and decreased photoinhibition in the presence of UVR. The thalli that received photosynthetically active radiation (PAR) treatment exhibited higher growth rates than those that received PAR + UVR at ambient or enhanced nitrate concentrations. However, under PAR + UVR treatment, the absorptivity of UVACs was higher than that of PAR and fluctuated with light levels. UVR was found to reduce the maximal net photosynthetic rate, apparent photosynthetic efficiency and light-saturating irradiance while increasing the dark respiration rate, and inducing higher inhibition of growth and photosynthesis under high light versus under low light. Ultraviolet B significantly induced the synthesis of UVACs but led to higher inhibition on growth and photosynthesis than ultraviolet A.
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- 2013
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12. IMPACTS OF SOLAR UV RADIATION ON THE PHOTOSYNTHESIS, GROWTH, AND UV-ABSORBING COMPOUNDS IN GRACILARIA LEMANEIFORMIS (RHODOPHYTA) GROWN AT DIFFERENT NITRATE CONCENTRATIONS(1)
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Yangqiao, Zheng and Kunshan, Gao
- Abstract
Solar ultraviolet radiation (UVR, 280-400 nm) is known to affect macroalgal physiology negatively, while nutrient availability may affect UV-absorbing compounds (UVACs) and sensitivity to UVR. However, little is known about the interactive effects of UVR and nitrate availability on macroalgal growth and photosynthesis. We investigated the growth and photosynthesis of the red alga Gracilaria lemaneiformis (Bory) Grev. at different levels of nitrate (natural or enriched nitrate levels of 41 or 300 and 600 μM) under different solar radiation treatments with or without UVR. Nitrate-enrichment enhanced the growth, resulted in higher concentrations of UVACs, and led to negligible photoinhibition of photosynthesis even at noon in the presence of UVR. Net photosynthesis during the noon period was severely inhibited by both ultraviolet-A radiation (UVA) and ultraviolet-B radiation (UVB) in the thalli grown in seawater without enriched nitrate. The absorptivity of UVACs changed in response to changes in the PAR dose when the thalli were shifted back and forth from solar radiation to indoor low light, and exposure to UVR significantly induced the synthesis of UVACs. The thalli exposed to PAR alone exhibited higher growth rates than those that received PAR + UVA or PAR + UVA + UVB at the ambient or enriched nitrate concentrations. UVR inhibited growth approximately five times as much as it inhibited photosynthesis within a range of 60-120 μg UVACs · g(-1) (fwt) when the thalli were grown under nitrate-enriched conditions. Such differential inhibition implies that other metabolic processes are more sensitive to solar UVR than photosynthesis.
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- 2016
13. Measurement of benthic photosynthesis and calcification in flowing-through seawater with stable carbonate chemistry
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Kunshan Gao, Yangqiao Zheng, Juntian Xu, and Caihuan Ke
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chemistry.chemical_compound ,Oceanography ,chemistry ,Benthic zone ,Basic research ,Carbonate ,Ocean Engineering ,Seawater ,Team project - Abstract
National Basic Research Program of China [2009CB421207]; National Natural Science Foundation of China [41120164007, 40930846]; Changjiang Scholars and Innovative Research Team project [IRT0941]; China-Japan collaboration project from MOST [S2012GR0290]; Ocean Commonweal Project [201205013]
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- 2012
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14. Impacts of chlorination and heat shocks on growth, pigments and photosynthesis of Phaeodactylum tricornutum (Bacillariophyceae)
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Yangqiao Zheng, Hongping Lin, Wei Li, Zhaoli Xu, Kunshan Gao, and Zengling Ma
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biology ,Ecology ,Environmental protection ,Phaeodactylum tricornutum ,Aquatic Science ,Photosynthesis ,biology.organism_classification ,Ecology, Evolution, Behavior and Systematics ,Primary productivity - Abstract
Changjiang Scholars and Innovative Research Team Program [IRT0941]; National Maritime Bureau's special fund for scientific research on public causes [200905010-13]; Special Research Fund for the National Non-profit Institutes [2008M15]; State Key Laborato
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- 2011
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15. IMPACTS OF SOLAR UV RADIATION ON THE PHOTOSYNTHESIS, GROWTH, AND UV-ABSORBING COMPOUNDS INGRACILARIA LEMANEIFORMIS(RHODOPHYTA) GROWN AT DIFFERENT NITRATE CONCENTRATIONS
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Kunshan Gao and Yangqiao Zheng
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Photoinhibition ,integumentary system ,Plant Science ,Aquatic Science ,Radiation ,Biology ,Photosynthesis ,Thallus ,chemistry.chemical_compound ,Nutrient ,Nitrate ,chemistry ,Aquatic plant ,Botany ,Seawater - Abstract
Solar ultraviolet radiation (UVR, 280-400 nm) is known to affect macroalgal physiology negatively, while nutrient availability may affect UV-absorbing compounds (UVACs) and sensitivity to UVR. However, little is known about the interactive effects of UVR and nitrate availability on macroalgal growth and photosynthesis. We investigated the growth and photosynthesis of the red alga Gracilaria lemaneiformis (Bory) Grev. at different levels of nitrate (natural or enriched nitrate levels of 41 or 300 and 600 μM) under different solar radiation treatments with or without UVR. Nitrate-enrichment enhanced the growth, resulted in higher concentrations of UVACs, and led to negligible photoinhibition of photosynthesis even at noon in the presence of UVR. Net photosynthesis during the noon period was severely inhibited by both ultraviolet-A radiation (UVA) and ultraviolet-B radiation (UVB) in the thalli grown in seawater without enriched nitrate. The absorptivity of UVACs changed in response to changes in the PAR dose when the thalli were shifted back and forth from solar radiation to indoor low light, and exposure to UVR significantly induced the synthesis of UVACs. The thalli exposed to PAR alone exhibited higher growth rates than those that received PAR + UVA or PAR + UVA + UVB at the ambient or enriched nitrate concentrations. UVR inhibited growth approximately five times as much as it inhibited photosynthesis within a range of 60-120 μg UVACs · g(-1) (fwt) when the thalli were grown under nitrate-enriched conditions. Such differential inhibition implies that other metabolic processes are more sensitive to solar UVR than photosynthesis.
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- 2009
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16. Combined effects of ocean acidification and solar UV radiation on photosynthesis, growth, pigmentation and calcification of the coralline alga Corallina sessilis (Rhodophyta).
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KUNSHAN GAO and YANGQIAO ZHENG
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OCEAN acidification , *ULTRAVIOLET radiation , *PHOTOSYNTHESIS , *BIOLOGICAL pigments , *ALGAE , *CORALS , *CORALLINE algae , *BIOMINERALIZATION , *CALCIFICATION - Abstract
Previous studies have shown that increasing atmospheric CO2 concentrations affect calcification in some planktonic and macroalgal calcifiers due to the changed carbonate chemistry of seawater. However, little is known regarding how calcifying algae respond to solar UV radiation (UVR, UVA+UVB, 280–400 nm). UVR may act synergistically, antagonistically or independently with ocean acidification (high CO2/low pH of seawater) to affect their calcification processes. We cultured the articulated coralline alga Corallina sessilis Yendo at 380 ppmv (low) and 1000 ppmv (high) CO2 levels while exposing the alga to solar radiation treatments with or without UVR. The presence of UVR inhibited the growth, photosynthetic O2 evolution and calcification rates by13%, 6% and 3% in the low and by 47%, 20% and 8% in the high CO2 concentrations, respectively, reflecting a synergistic effect of CO2 enrichment with UVR. UVR induced significant decline of pH in the CO2-enriched cultures. The contents of key photosynthetic pigments, chlorophyll a and phycobiliproteins decreased, while UV-absorptivity increased under the high pCO2/low pH condition. Nevertheless, UV-induced inhibition of photosynthesis increased when the ratio of particulate inorganic carbon/particulate organic carbon decreased under the influence of CO2-acidified seawater, suggesting that the calcified layer played a UV-protective role. Both UVA and UVB negatively impacted photosynthesis and calcification, but the inhibition caused by UVB was about 2.5–2.6 times that caused by UVA. The results imply that coralline algae suffer from more damage caused by UVB as they calcify less and less with progressing ocean acidification. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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