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Cheng YY, Gregorich Z, Prajnamitra RP, Lundy DJ, Ma TY, Huang YH, Lee YC, Ruan SC, Lin JH, Lin PJ, Kuo CW, Chen P, Yan YT, Tian R, Kamp TJ, Hsieh PC. Metabolic Changes Associated With Cardiomyocyte Dedifferentiation Enable Adult Mammalian Cardiac Regeneration. Circulation 2022; 146:1950-1967. [PMID: 36420731 PMCID: PMC9808601 DOI: 10.1161/circulationaha.122.061960] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 09/29/2022] [Indexed: 11/25/2022]
Abstract
BACKGROUND Cardiac regeneration after injury is limited by the low proliferative capacity of adult mammalian cardiomyocytes (CMs). However, certain animals readily regenerate lost myocardium through a process involving dedifferentiation, which unlocks their proliferative capacities. METHODS We bred mice with inducible, CM-specific expression of the Yamanaka factors, enabling adult CM reprogramming and dedifferentiation in vivo. RESULTS Two days after induction, adult CMs presented a dedifferentiated phenotype and increased proliferation in vivo. Microarray analysis revealed that upregulation of ketogenesis was central to this process. Adeno-associated virus-driven HMGCS2 overexpression induced ketogenesis in adult CMs and recapitulated CM dedifferentiation and proliferation observed during partial reprogramming. This same phenomenon was found to occur after myocardial infarction, specifically in the border zone tissue, and HMGCS2 knockout mice showed impaired cardiac function and response to injury. Finally, we showed that exogenous HMGCS2 rescues cardiac function after ischemic injury. CONCLUSIONS Our data demonstrate the importance of HMGCS2-induced ketogenesis as a means to regulate metabolic response to CM injury, thus allowing cell dedifferentiation and proliferation as a regenerative response.
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Affiliation(s)
- Yuan-Yuan Cheng
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Zachery Gregorich
- Department of Medicine and Stem Cell and Regenerative Medicine Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705, USA
| | | | - David J. Lundy
- Graduate Institute of Biomedical Materials and Tissue Engineering, Taipei Medical University, Taipei 110, Taiwan
| | - Ting-Yun Ma
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Yu-Hsuan Huang
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Yi-Chan Lee
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Shu-Chian Ruan
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Jen-Hao Lin
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Po-Ju Lin
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Chiung Wen Kuo
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Peilin Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Yu-Ting Yan
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Rong Tian
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine and Department of Bioengineering, University of Washington, Seattle, WA 98109, USA
| | - Timothy J. Kamp
- Department of Medicine and Stem Cell and Regenerative Medicine Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Patrick C.H. Hsieh
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
- Department of Medicine and Stem Cell and Regenerative Medicine Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705, USA
- Graduate Institute of Medical Genomics and Proteomics and Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei 100, Taiwan
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2
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Shih CP, Tang X, Kuo CW, Chueh DY, Chen P. Design principles of bioinspired interfaces for biomedical applications in therapeutics and imaging. Front Chem 2022; 10:990171. [PMID: 36405322 PMCID: PMC9673126 DOI: 10.3389/fchem.2022.990171] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Accepted: 09/08/2022] [Indexed: 09/29/2023] Open
Abstract
In the past two decades, we have witnessed rapid developments in nanotechnology, especially in biomedical applications such as drug delivery, biosensing, and bioimaging. The most commonly used nanomaterials in biomedical applications are nanoparticles, which serve as carriers for various therapeutic and contrast reagents. Since nanomaterials are in direct contact with biological samples, biocompatibility is one of the most important issues for the fabrication and synthesis of nanomaterials for biomedical applications. To achieve specific recognition of biomolecules for targeted delivery and biomolecular sensing, it is common practice to engineer the surfaces of nanomaterials with recognition moieties. This mini-review summarizes different approaches for engineering the interfaces of nanomaterials to improve their biocompatibility and specific recognition properties. We also focus on design strategies that mimic biological systems such as cell membranes of red blood cells, leukocytes, platelets, cancer cells, and bacteria.
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Affiliation(s)
- Chun-Pei Shih
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Xiaofang Tang
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Chiung Wen Kuo
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Di-Yen Chueh
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Peilin Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
- Institute of Physics, Academia Sinica, Taipei, Taiwan
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3
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Kuo CW, Pratiwi FW, Liu YT, Chueh DY, Chen P. Revealing the nanometric structural changes in myocardial infarction models by time-lapse intravital imaging. Front Bioeng Biotechnol 2022; 10:935415. [PMID: 36051583 PMCID: PMC9424828 DOI: 10.3389/fbioe.2022.935415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 07/25/2022] [Indexed: 11/13/2022] Open
Abstract
In the development of bioinspired nanomaterials for therapeutic applications, it is very important to validate the design of nanomaterials in the disease models. Therefore, it is desirable to visualize the change of the cells in the diseased site at the nanoscale. Heart diseases often start with structural, morphological, and functional alterations of cardiomyocyte components at the subcellular level. Here, we developed straightforward technique for long-term real-time intravital imaging of contracting hearts without the need of cardiac pacing and complex post processing images to understand the subcellular structural and dynamic changes in the myocardial infarction model. A two-photon microscope synchronized with electrocardiogram signals was used for long-term in vivo imaging of a contracting heart with subcellular resolution. We found that the structural and dynamic behaviors of organelles in cardiomyocytes closely correlated with heart function. In the myocardial infarction model, sarcomere shortening decreased from ∼15% (healthy) to ∼8% (diseased) as a result of impaired cardiac function, whereas the distances between sarcomeres increased by 100 nm (from 2.11 to 2.21 μm) in the diastolic state. In addition, T-tubule system regularity analysis revealed that T-tubule structures that were initially highly organized underwent significant remodeling. Morphological remodeling and changes in dynamic activity at the subcellular level are essential to maintain heart function after infarction in a heart disease model.
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Affiliation(s)
- Chiung Wen Kuo
- Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
| | | | - Yen-Ting Liu
- Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
| | - Di-Yen Chueh
- Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
| | - Peilin Chen
- Research Center for Applied Science, Academia Sinica, Taipei, Taiwan
- Institute of Physics, Academia Sinica, Taipei, Taiwan
- *Correspondence: Peilin Chen,
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4
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Huang SS, Lee KJ, Chen HC, Prajnamitra RP, Hsu CH, Jian CB, Yu XE, Chueh DY, Kuo CW, Chiang TC, Choong OK, Huang SC, Beh CY, Chen LL, Lai JJ, Chen P, Kamp TJ, Tien YW, Lee HM, Hsieh PCH. Immune cell shuttle for precise delivery of nanotherapeutics for heart disease and cancer. Sci Adv 2021; 7:7/17/eabf2400. [PMID: 33893103 PMCID: PMC8064633 DOI: 10.1126/sciadv.abf2400] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 03/05/2021] [Indexed: 05/05/2023]
Abstract
The delivery of therapeutics through the circulatory system is one of the least arduous and less invasive interventions; however, this approach is hampered by low vascular density or permeability. In this study, by exploiting the ability of monocytes to actively penetrate into diseased sites, we designed aptamer-based lipid nanovectors that actively bind onto the surface of monocytes and are released upon reaching the diseased sites. Our method was thoroughly assessed through treating two of the top causes of death in the world, cardiac ischemia-reperfusion injury and pancreatic ductal adenocarcinoma with or without liver metastasis, and showed a significant increase in survival and healing with no toxicity to the liver and kidneys in either case, indicating the success and ubiquity of our platform. We believe that this system provides a new therapeutic method, which can potentially be adapted to treat a myriad of diseases that involve monocyte recruitment in their pathophysiology.
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Affiliation(s)
- San-Shan Huang
- Ph.D. Program in Translational Medicine, National Taiwan University and Academia Sinica, Taipei, Taiwan
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Keng-Jung Lee
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Hung-Chih Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | | | - Chia-Hsin Hsu
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Cheng-Bang Jian
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
- Department of Chemistry, National Taiwan University, Taipei 115, Taiwan
- Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Taiwan University, Taipei, Taiwan
| | - Xu-En Yu
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
- Department of Chemistry, National Central University, Chung-Li 32001, Taiwan
| | - Di-Yen Chueh
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Chiung Wen Kuo
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Tsai-Chen Chiang
- Department of Surgery, National Taiwan University and Hospital, Taipei 100, Taiwan
| | - Oi Kuan Choong
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Shao-Chan Huang
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Chaw Yee Beh
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Li-Lun Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - James J Lai
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | - Peilin Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Timothy J Kamp
- Department of Medicine and Stem Cell and Regenerative Medicine Center, University of Wisconsin, Madison, WI 53705, USA
| | - Yu-Wen Tien
- Department of Surgery, National Taiwan University and Hospital, Taipei 100, Taiwan
| | - Hsien-Ming Lee
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
| | - Patrick Ching-Ho Hsieh
- Ph.D. Program in Translational Medicine, National Taiwan University and Academia Sinica, Taipei, Taiwan.
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
- Department of Medicine and Stem Cell and Regenerative Medicine Center, University of Wisconsin, Madison, WI 53705, USA
- Institute of Medical Genomics and Proteomics and Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei 100, Taiwan
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Pratiwi FW, Peng CC, Wu SH, Kuo CW, Mou CY, Tung YC, Chen P. Evaluation of Nanoparticle Penetration in the Tumor Spheroid Using Two-Photon Microscopy. Biomedicines 2020; 9:10. [PMID: 33374319 PMCID: PMC7824314 DOI: 10.3390/biomedicines9010010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/21/2020] [Accepted: 12/22/2020] [Indexed: 12/23/2022] Open
Abstract
Mesoporous silica nanoparticles (MSNs) have emerged as a prominent nanomedicine platform, especially for tumor-related nanocarrier systems. However, there is increasing concern about the ability of nanoparticles (NPs) to penetrate solid tumors, resulting in compromised antitumor efficacy. Because the physicochemical properties of NPs play a significant role in their penetration and accumulation in solid tumors, it is essential to systematically study their relationship in a model system. Here, we report a multihierarchical assessment of the accumulation and penetration of fluorescence-labeled MSNs with nine different physicochemical properties in tumor spheroids using two-photon microscopy. Our results indicated that individual physicochemical parameters separately could not define the MSNs' ability to accumulate in a deeper tumor region; their features are entangled. We observed that the MSNs' stability determined their success in reaching the hypoxia region. Moreover, the change in the MSNs' penetration behavior postprotein crowning was associated with both the original properties of NPs and proteins on their surfaces.
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Affiliation(s)
- Feby Wijaya Pratiwi
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan; (F.W.P.); (C.-C.P.); (C.W.K.); (Y.-C.T.)
| | - Chien-Chung Peng
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan; (F.W.P.); (C.-C.P.); (C.W.K.); (Y.-C.T.)
| | - Si-Han Wu
- Graduate Institute of Nanomedicine and Medical Engineering, Taipei Medical University, Taipei 11031, Taiwan;
| | - Chiung Wen Kuo
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan; (F.W.P.); (C.-C.P.); (C.W.K.); (Y.-C.T.)
| | - Chung-Yuan Mou
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan;
| | - Yi-Chung Tung
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan; (F.W.P.); (C.-C.P.); (C.W.K.); (Y.-C.T.)
| | - Peilin Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan; (F.W.P.); (C.-C.P.); (C.W.K.); (Y.-C.T.)
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6
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Abstract
Rapid and recent progress in fluorescence microscopic techniques has allowed for routine discovery and viewing of biological structures and processes in unprecedented spatiotemporal resolution. In these imaging techniques, fluorescent nanoparticles (NPs) play important roles in the improvement of reporting systems. A short overview of recently developed fluorescent NPs used for advanced in vivo imaging will be discussed in this mini-review. The discussion begins with the contribution of fluorescence imaging in exploring the fate of NPs in biological systems. NP applications for in vivo imaging, including cell labeling, multimodal imaging and theranostic agents, are then discussed. Finally, despite all of the advancements in bioimaging, some unsolved challenges will be briefly discussed concerning future research directions.
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Affiliation(s)
| | - Chiung Wen Kuo
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Bi-Chang Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Peilin Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
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7
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Kuo CW, Chueh DY, Chen P. Real-time in vivo imaging of subpopulations of circulating tumor cells using antibody conjugated quantum dots. J Nanobiotechnology 2019; 17:26. [PMID: 30728024 PMCID: PMC6364392 DOI: 10.1186/s12951-019-0453-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 01/10/2019] [Indexed: 12/14/2022] Open
Abstract
INTRODUCTION The detection of circulating tumor cells (CTCs) is very important for cancer diagnosis. CTCs can travel from primary tumors through the circulation to form secondary tumor colonies via bloodstream extravasation. The number of CTCs has been used as an indicator of cancer progress. However, the population of CTCs is very heterogeneous. It is very challenging to identify CTC subpopulations such as cancer stem cells (CSCs) with high metastatic potential, which are very important for cancer diagnostic management. RESULTS We report a study of real-time CTC and CSC imaging in the bloodstreams of living animals using multi-photon microscopy and antibody conjugated quantum dots. We have developed a cancer model for noninvasive imaging wherein pancreatic cancer cells expressing fluorescent proteins were subcutaneously injected into the earlobes of mice and then formed solid tumors. When the cancer cells broke away from the solid tumor, CTCs with fluorescent proteins in the bloodstream at different stages of development could be monitored noninvasively in real time. The number of CTCs observed in the blood vessels could be correlated to the tumor size in the first month and reached a maximum value of approximately 100 CTCs/min after 5 weeks of tumor inoculation. To observe CTC subpopulations, conjugated quantum dots were used. It was found that cluster of differentiation (CD)24+ CTCs can move along the blood vessel walls and migrate to peripheral tissues. CD24+ cell accumulation on the solid tumors' sides was observed, which may provide valuable insight for designing new drugs to target cancer subpopulations with high metastatic potential. We also demonstrated that our system is capable of imaging a minor population of cancer stem cells, CD133+ CTCs, which are found in 0.7% of pancreatic cancer cells and 1%-3% of solid tumors in patients. CONCLUSIONS With the help of quantum dots, CTCs with higher metastatic potential, such as CD24+ and CD133+ CTCs, have been identified in living animals. Using our approach, it may be possible to investigate detailed metastatic mechanism such as tumor cell extravasation to the blood vessels. In addition, the number of observed CTCs in the blood stream could be correlated with tumor stage in the early stage of cancer.
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Affiliation(s)
- Chiung Wen Kuo
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Di-Yen Chueh
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Peilin Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan.
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Sarkar S, Peng CC, Kuo CW, Chueh DY, Wu HM, Liu YH, Chen P, Tung YC. Study of oxygen tension variation within live tumor spheroids using microfluidic devices and multi-photon laser scanning microscopy. RSC Adv 2018; 8:30320-30329. [PMID: 35546825 PMCID: PMC9085395 DOI: 10.1039/c8ra05505j] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 08/21/2018] [Indexed: 11/24/2022] Open
Abstract
Three-dimensional cell spheroid culture using microfluidic devices provides a convenient in vitro model for studying tumour spheroid structures and internal microenvironments. Recent studies suggest that oxygen deprived zones inside solid tumors are responsible for stimulating local cytokines and endothelial vasculature proliferation during angiogenesis. In this work, we develop an integrated approach combining microfluidic devices and multi-photon laser scanning microscopy (MPLSM) to study variations in oxygen tension within live spheroids of human osteosarcoma cells. Uniform shaped, size-controlled spheroids are grown and then harvested using a polydimethylsiloxane (PDMS) based microfluidic device. Fluorescence live imaging of the harvested spheroids is performed using MPLSM and a commercially available oxygen sensitive dye, Image-iT Red, to observe the oxygen tension variation within the spheroids and those co-cultured with monolayers of human umbilical vein endothelial cells (HUVECs). Oxygen tension variations are observed within the spheroids with diameters ranging from 90 ± 10 μm to 140 ± 10 μm. The fluorescence images show that the low-oxygenated cores diminish when spheroids are co-cultured with HUVEC monolayers for 6 hours to 8 hours. In the experiments, spheroids subjected to HUVEC conditioned medium treatment and with a cell adherent substrate are also measured and analyzed to study their significance on oxygen tension within the spheroids. The results show that the oxygenation within the spheroids is improved when the spheroids are cultured under those conditions. Our work presents an efficient method to study oxygen tension variation within live tumor spheroids under the influence of endothelial cells and conditioned medium. The method can be exploited for further investigation of tumor oxygen microenvironments during angiogenesis. This paper reports an integrated approach combining microfluidic devices and multi-photon laser scanning microscopy (MPLSM) to study variations in oxygen tension within live spheroids of human osteosarcoma cells under various culture conditions.![]()
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Affiliation(s)
- Sreerupa Sarkar
- Department of Engineering and System Science
- National Tsing Hua University
- Hsinchu 30013
- Taiwan
- Research Center for Applied Sciences
| | - Chien-Chung Peng
- Research Center for Applied Sciences
- Academia Sinica
- Taipei 11529
- Taiwan
| | - Chiung Wen Kuo
- Research Center for Applied Sciences
- Academia Sinica
- Taipei 11529
- Taiwan
| | - Di-Yen Chueh
- Research Center for Applied Sciences
- Academia Sinica
- Taipei 11529
- Taiwan
| | - Hsiao-Mei Wu
- Research Center for Applied Sciences
- Academia Sinica
- Taipei 11529
- Taiwan
| | - Yuan-Hsuan Liu
- Research Center for Applied Sciences
- Academia Sinica
- Taipei 11529
- Taiwan
| | - Peilin Chen
- Research Center for Applied Sciences
- Academia Sinica
- Taipei 11529
- Taiwan
| | - Yi-Chung Tung
- Research Center for Applied Sciences
- Academia Sinica
- Taipei 11529
- Taiwan
- Taiwan International Graduate Program (TIGP)
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Abstract
Flexible polymer nanopillar substrates were used to systematically demonstrate cell alignment and migration guided by the directional formation of focal adhesions. The polymer nanopillar substrates were constructed to various height specifications to provide an extensive variation of flexibility; a rectangular arrangement created spatial confinement between adjacent nanopillars, providing less spacing in the horizontal and vertical directions. Three polymer nanopillar substrates with the diameter of 400 nm and the heights of 400, 800, and 1200 nm were fabricated. Super-resolution localization imaging and protein pair-distance analysis of vinculin proteins revealed that Chinese hamster ovary (CHO) cells formed mature focal adhesions on 1200 nm high nanopillar substrates by bending adjacent nanopillars to link dot-like adhesions. The spacing confinement of the adjacent nanopillars enhanced the orthogonal directionality of the formation tendency of the mature focal adhesions. The directional formation of the mature focal adhesions also facilitated the organization of actin filaments in the horizontal and vertical directions. Moreover, 78% of the CHO cells were aligned in these two directions, in conformity with the flexibility and nanotopographical cues of the nanopillars. Biased cell migration was observed on the 1200 nm high nanopillar substrates.
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Affiliation(s)
- Fan-Ching Chien
- Department of Optics and Photonics, National Central University, Taoyuan 32001, Taiwan
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10
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Pratiwi FW, Hsia CH, Kuo CW, Yang SM, Hwu YK, Chen P. Construction of single fluorophore ratiometric pH sensors using dual-emission Mn2+-doped quantum dots. Biosens Bioelectron 2016; 84:133-40. [DOI: 10.1016/j.bios.2016.01.079] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 01/26/2016] [Accepted: 01/28/2016] [Indexed: 01/04/2023]
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Chatterjee K, Kuo CW, Chen A, Chen P. Detection of residual rifampicin in urine via fluorescence quenching of gold nanoclusters on paper. J Nanobiotechnology 2015; 13:46. [PMID: 26113082 PMCID: PMC4482266 DOI: 10.1186/s12951-015-0105-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/17/2015] [Indexed: 01/08/2023] Open
Abstract
Background Rifampicin or rifampin (R) is a common drug used to treat inactive meningitis, cholestatic pruritus and tuberculosis (TB), and it is generally prescribed for long-term administration under regulated dosages. Constant monitoring of rifampicin is important for controlling the side effects and preventing overdose caused by chronic medication. In this study, we present an easy to use, effective and less costly method for detecting residual rifampicin in urine samples using protein (bovine serum albumin, BSA)-stabilized gold nanoclusters (BSA-Au NCs) adsorbed on a paper substrate in which the concentration of rifampicin in urine can be detected via fluorescence quenching. The intensity of the colorimetric assay performed on the paper-based platforms can be easily captured using a digital camera and subsequently analyzed. Results The decreased fluorescence intensity of BSA-Au NCs in the presence of rifampicin allows for the sensitive detection of rifampicin in a range from 0.5 to 823 µg/mL. The detection limit for rifampicin was measured as 70 ng/mL. The BSA-Au NCs were immobilized on a wax-printed paper-based platform and used to conduct real-time monitoring of rifampicin in urine. Conclusion We have developed a robust, cost-effective, and portable point-of-care medical diagnostic platform for the detection of rifampicin in urine based on the ability of rifampicin to quench the fluorescence of immobilized BSA-Au NCs on wax-printed papers. The paper-based assay can be further used for the detection of other specific analytes via surface modification of the BSA in BSA-Au NCs and offers a useful tool for monitoring other diseases. Electronic supplementary material The online version of this article (doi:10.1186/s12951-015-0105-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Krishnendu Chatterjee
- Department of Engineering and System Science, National Tsing Hua University, Hsinchu, 300, Taiwan. .,Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 115, Taiwan. .,National Tsing Hua University, Hsinchu, 300, Taiwan. .,Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan, ROC.
| | - Chiung Wen Kuo
- Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan, ROC.
| | - Ann Chen
- Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
| | - Peilin Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, 115, Taiwan, ROC.
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12
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Abstract
BACKGROUND Cells explore the surfaces of materials through membrane-bound receptors, such as the integrins, and use them to interact with extracellular matrix molecules adsorbed on the substrate surfaces, resulting in the formation of focal adhesions. With recent advances in nanotechnology, biosensors and bioelectronics are being fabricated with ever decreasing feature sizes. The performances of these devices depend on how cells interact with nanostructures on the device surfaces. However, the behavior of cells on nanostructures is not yet fully understood. Here we present a systematic study of cell-nanostructure interaction using polymeric nanopillars with various diameters. RESULTS We first checked the viability of cells grown on nanopillars with diameters ranging from 200 nm to 700 nm. It was observed that when cells were cultured on the nanopillars, the apoptosis rate slightly increased as the size of the nanopillar decreased. We then calculated the average size of the focal adhesions and the cell-spreading area for focal adhesions using confocal microscopy. The size of focal adhesions formed on the nanopillars was found to decrease as the size of the nanopillars decreased, resembling the formations of nascent focal complexes. However, when the size of nanopillars decreased to 200 nm, the size of the focal adhesions increased. Further study revealed that cells interacted very strongly with the nanopillars with a diameter of 200 nm and exerted sufficient forces to bend the nanopillars together, resulting in the formation of larger focal adhesions. CONCLUSIONS We have developed a simple approach to systematically study cell-substrate interactions on physically well-defined substrates using size-tunable polymeric nanopillars. From this study, we conclude that cells can survive on nanostructures with a slight increase in apoptosis rate and that cells interact very strongly with smaller nanostructures. In contrast to previous observations on flat substrates that cells interacted weakly with softer substrates, we observed strong cell-substrate interactions on the softer nanopillars with smaller diameters. Our results indicate that in addition to substrate rigidity, nanostructure dimensions are additional important physical parameters that can be used to regulate behaviour of cells.
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Affiliation(s)
- Chiung Wen Kuo
- Research Center for Applied Sciences, Academia Sinica, 128, Section 2, Academia Road, Nankang, Taipei, 11529, Taiwan.
| | - Di-Yen Chueh
- Research Center for Applied Sciences, Academia Sinica, 128, Section 2, Academia Road, Nankang, Taipei, 11529, Taiwan.
| | - Peilin Chen
- Research Center for Applied Sciences, Academia Sinica, 128, Section 2, Academia Road, Nankang, Taipei, 11529, Taiwan.
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Cheng SM, Chang YC, Liu CY, Lee JYC, Chan HH, Kuo CW, Lin KY, Tsai SL, Chen SH, Li CF, Leung E, Kanwar JR, Huang CC, Chang JY, Cheung CHA. YM155 down-regulates survivin and XIAP, modulates autophagy and induces autophagy-dependent DNA damage in breast cancer cells. Br J Pharmacol 2014; 172:214-34. [PMID: 25220225 DOI: 10.1111/bph.12935] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 08/14/2014] [Accepted: 09/08/2014] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND AND PURPOSE The aim of this study was to determine the potency and molecular mechanism of action of YM155, a first-in-class survivin inhibitor that is currently under phase I/II clinical investigations, in various drug-resistant breast cancers including the oestrogen receptor positive (ER(+) ) tamoxifen-resistant breast cancer and the caspase-3-deficient breast cancer. EXPERIMENTAL APPROACH The potency of YM155 in SK-BR-3, MDA-MB-231, MCF7 and its tamoxifen-resistant sublines, TamR6, TamR7, TamR8, TamC3 and TamC6, were determined by MTT assay. Western blot analysis, flow cytometric analysis, reverse transcription-PCR, fluorescent microscopy and comet assay were used to determine the molecular mechanism of action of YM155 in different breast cancer cell lines. KEY RESULTS YM155 was equally potent towards the parental ER(+) /caspase-3-deficient MCF7 breast cancer cells and its tamoxifen-resistant sublines in vitro. The ER(-) /HER2(+) SK-BR-3 breast cancer cells and the triple-negative/caspase-3-expressing metastatic aggressive MDA-MB-231 breast cancer cells were also sensitive to YM155 with IC50 values in the low nanomolar range. Targeting survivin by YM155 modulated autophagy, induced autophagy-dependent caspase-7 activation and autophagy-dependent DNA damage in breast cancer cells. Interestingly, YM155 also induced XIAP degradation and the degradation of XIAP might play an important role in YM155-induced autophagy in breast cancer cells. CONCLUSIONS AND IMPLICATIONS YM155 is a potent survivin inhibitor that has potential for the management of various breast cancer subtypes regardless of the expression of ER, HER2 and caspase-3. Importantly, this study provides new insights into YM155's molecular mechanism of action and therapeutic potential in the treatment of tamoxifen-resistant breast cancer.
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Affiliation(s)
- S M Cheng
- The Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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Charan S, Sanjiv K, Singh N, Chien FC, Chen YF, Nergui NN, Huang SH, Kuo CW, Lee TC, Chen P. Development of Chitosan Oligosaccharide-Modified Gold Nanorods for in Vivo Targeted Delivery and Noninvasive Imaging by NIR Irradiation. Bioconjug Chem 2012; 23:2173-82. [DOI: 10.1021/bc3001276] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shobhit Charan
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan
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Chien FC, Kuo CW, Yang ZH, Chueh DY, Chen P. Exploring the formation of focal adhesions on patterned surfaces using super-resolution imaging. Small 2011; 7:2906-2913. [PMID: 21861294 DOI: 10.1002/smll.201100753] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 06/15/2011] [Indexed: 05/31/2023]
Abstract
The formation of focal adhesions on various sizes of fibronectin patterns, ranging from 200 μm to 250 nm, was systematically investigated by total internal reflection fluorescence microscopy and super-resolution imaging. It was found that cells adhered to and spread on these micro/nanopatterns, forming focal adhesions. On a micrometer scale the shape of the focal adhesions was elongated. However, on the nanometer scale, the shape of focal adhesions became dotlike. To further explore the distribution of focal adhesion proteins formed on surfaces, a localization-based super-resolution imaging technique was employed in order to determine the position and density of vinculin proteins. A characteristic distance of 50 nm was found between vinculin molecules in the focal adhesions, which did not depend on the size of the fibronectin nanopatterns. This distance was found to be crucial for the formation of focal adhesions. In addition, the density of vinculin at the focal adhesions formed on the nanopatterns increased as the pattern size decreased. The density of the protein was found to be 425 ± 247, 584 ± 302, and 703 ± 305 proteins μm(-2) on the 600, 400, and 250 nm fibronectin patterns respectively. Whereas 226 ± 77 proteins μm(-2) was measured for the matured focal adhesions on homogeneous fibronectin coated substrates. The increase in vinculin density implies that an increase in mechanical load was applied to the focal adhesions formed on the smaller nanopatterns.
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Affiliation(s)
- Fan-Ching Chien
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
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Kuo CW, Chien FC, Shiu JY, Tsai SM, Chueh DY, Hsiao YS, Yang ZH, Chen P. Investigation of the growth of focal adhesions using protein nanoarrays fabricated by nanocontact printing using size tunable polymeric nanopillars. Nanotechnology 2011; 22:265302. [PMID: 21576808 DOI: 10.1088/0957-4484/22/26/265302] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Here we describe a simple approach to create various sizes of protein nanoarrays for the investigation of cell adhesion. Using a combination of nanosphere lithography, oxygen plasma treatment, deep etching and nanomolding processes, well-ordered polymeric nanopillar arrays have been fabricated with diameters in the range of 50-600 nm. These nanopillar arrays were used as stamps for nanocontact printing to create fibronectin nanoarrays, which were used to study the size dependent formation of focal adhesion. It was found that cells can adhere and spread on fibronectin nanoarrays with a fibronectin pattern as small as 50 nm. It was also found that the average size of focal adhesion decreased as the size of the fibronectin pattern was reduced.
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Affiliation(s)
- Chiung Wen Kuo
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
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Chien FC, Huang WY, Shiu JY, Kuo CW, Chen P. Revealing the spatial distribution of the site enhancement for the surface enhanced Raman scattering on the regular nanoparticle arrays. Opt Express 2009; 17:13974-13981. [PMID: 19654805 DOI: 10.1364/oe.17.013974] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The spatial distribution of the site enhancement for the surface-enhanced Raman scattering (SERS) on the regular nanoparticle arrays has been investigated by the confocal Raman microscopy. It was found that the spatial distribution of the Raman signals on the well-ordered nanoparticle arrays was very inhomogeneous and concentrated on the defects of the nanoparticle arrays. The SERS signals were also observed to depend on the thickness of silver film and the defect density. It has been demonstrated that the number of SERS active sites can be increased ten folds by trimming the size of nanoparticles using oxygen plasma.
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Affiliation(s)
- Fan-Ching Chien
- Research Center for Applied Sciences, Academia Sinica, 128, Section Nankang, Taipei 115, Taiwan
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Li Q, Kuo CW, Yang Z, Chen P, Chou KC. Surface-enhanced IR–visible sum frequency generation vibrational spectroscopy. Phys Chem Chem Phys 2009; 11:3436-42. [DOI: 10.1039/b821045d] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
STUDY OBJECTIVE A cancer registry was analyzed to determine if the clinicopathologic characteristics, treatment modalities, and prognosis of non-small cell lung cancer (NSCLC) patients < 40 years of age at diagnosis differed from patients > 80 years of age at diagnosis. DESIGN Retrospective review of patients with NSCLC diagnosed between 1987 and 1996. SETTING General teaching hospital in Taiwan. PATIENTS There were 6,048 cases of NSCLC diagnosed during this period. Among them, 127 patients were < 40 years old and 184 patients were > 80 years old. These patients were selected for our study. MEASUREMENTS Data regarding demographics, presentation symptoms, histology, tumor staging, treatment modality, and survival were obtained from all patients. Pearson's chi(2) test and the Kaplan-Meier method with a log-rank test were used for statistical analysis. RESULTS We found significantly more female patients (p < 0.001) and adenocarcinoma (p < 0.001) in the younger group, when compared with the older patients. Cough was the most frequent presenting symptom in both age groups, followed by dyspnea, chest pain, and hemoptysis. There was no statistical difference in the severity of the disease in terms of staging between the two age groups. Young patients received surgical intervention more frequently than the aged (p = 0.025). The older patients received only supportive care more frequently (p = 0.011) than the younger patients. Survival was better in young patients, when compared with other patients or aged patients (p < 0.001). CONCLUSIONS The female sex and adenocarcinoma were predominant in young NSCLC patients, when compared with the older patients. Young NSCLC patients tended to receive more aggressive treatment and had better survival.
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Affiliation(s)
- C W Kuo
- Chest Department, Veterans General Hospital-Taipei, and School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
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Abstract
Tracheal bronchus is a rarely found congenital bronchial anomaly. It usually originates from the right lateral wall of the trachea at the level < 2 cm above the tracheal bifurcation. The patients usually are asymptomatic, but some may experience recurrent pneumonia, chronic bronchitis, or bronchiectasis. It is very rare for a malignant tumor to grow from this aberrant bronchus. There are only four cases of lung cancer developing from the tracheal bronchus reported in the world literature, and we present a fifth case.
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Affiliation(s)
- C W Kuo
- Chest Department, Veterans General Hospital-Taipei, Taipei, Taiwan.
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Khoo KH, Jarboe E, Barker A, Torrelles J, Kuo CW, Chatterjee D. Altered expression profile of the surface glycopeptidolipids in drug-resistant clinical isolates of Mycobacterium avium complex. J Biol Chem 1999; 274:9778-85. [PMID: 10092667 DOI: 10.1074/jbc.274.14.9778] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the Mycobacterium avium complex are the most frequently encountered opportunistic bacterial pathogens among patients in the advanced stage of AIDS. Two clinical isolates of the same strain, numbers 397 and 417, were obtained from an AIDS patient with disseminated M. avium complex infection before and after treatment with a regimen of clarithromycin and ethambutol. To identify the biochemical consequence of drug treatment, the expression and chemical composition of their major cell wall constituents, the arabinogalactan, lipoarabinomannan, and the surface glycopeptidolipids (GPL), were critically examined. Through thin layer chromatography, mass spectrometry, and chemical analysis, it was found that the GPL expression profiles differ significantly in that several apolar GPLs were overexpressed in the clinically resistant 417 isolate at the expense of the serotype 1 polar GPL, which was the single predominant band in the ethambutol-susceptible 397 isolate. Thus, instead of additional rhamnosylation on the 6-deoxytalose (6-dTal) appendage to give the serotype 1-specific disaccharide hapten, the accumulation of this nonextended apolar GPL probably provided more precursor substrate available for further nonsaccharide substitutions including a higher degree of O-methylation to give 3-O-Me-6-dTal and the unusual 4-O-sulfation on 6-dTal. Further data showed that this alteration effectively neutralized ethambutol, which is known to inhibit arabinan synthesis. Thus, in contrast with derived Emb-resistant mutants of Mycobacterium smegmatis or Mycobacterium tuberculosis, which are devoid of a surface GPL layer, the lipoarabinomannan from resistant 417 isolate grown in the presence of this drug was not apparently truncated.
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Affiliation(s)
- K H Khoo
- Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan, Republic of China
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Abstract
The stiffness and strength of cancellous bone are important in the management of skeletal diseases such as osteoporosis. These properties are a function not only of bone density but also of bone architecture, some measure of which can be provided by quantitative ultrasound. The ability of quantitative ultrasound and bone mineral density (BMD) to predict stiffness and strength of human femoral heads removed from live subjects during hip replacement was assessed. Stiffness and strength were measured using a uniaxial compression test. Ultrasound velocity was measured using the pulse-submersion technique (McCue CUBAResearch) and BMD using DXA (Lunar DPX-L). Ultrasound velocity (quantitative ultrasound) and stiffness varied with the three orthogonal directions, the highest significance being between the proximo-distal (PD) and antero-posterior (AP) directions (p < 0.0001 for stiffness and p = 0.0003 for velocity). Ultrasound velocity was significantly correlated with compressive bone strength (r = 0.76, p < 0.0001) and stiffness (r = 0.79-0.83, p < 0.0001). BMD was also significantly correlated with compressive strength (r = 0.82, p < 0.0001) and stiffness (r = 0.66-0.81. p < 0.001). Using multiple regression analysis both BMD and velocity were significant predictors of strength (r = 0.88, p = 0.0004 and 0.0054 respectively) and stiffness (r = 0.92, p = 0.0001 and 0.0003 respectively). BMD and velocity were still independent significant predictors of both stiffness (r = 0.93, p < 0.0001 and 0.0001 respectively) and strength (r = 0.89, p < 0.0001 and 0.02) when they were combined as a product (BMDn*Vm). This suggests that BMD measured using DXA, if used in conjunction with ultrasound velocity, may be able to improve osteoporosis risk assessment. The information about femur anisotropy may also be important for hip prosthesis and in vivo modelling.
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Affiliation(s)
- C F Njeh
- Bone Densitometry Service, Queen Elizabeth Hospital, Birmingham, UK.
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Abstract
Two filamentous phages of Xanthomonas campestris pv. vesicatoria and Xanthomonas oryzae pv. oryzae were isolated and designated phi Xv and phi Xo, respectively. They were similar to other filamentous phages of Xanthomonas in (i) shape, (ii) restrictive host specificity, (iii) high stability, (iv) an ssDNA genome, (v) a dsDNA as the replicative form (RF), (vi) propagation without lysis of host cells and (vii) ability to integrate into the host chromosome. These phages showed sequence homology to filamentous phage phi Lf of X. c. pv. campestris. phi Xv was inactivated by antisera against phi Xv, phi Xo and phi Lf, whereas phi Xo and phi Lf were inactivated only by their respective antisera and the anti-phi Xv serum. Both the single-stranded phage DNAs and the RF DNAs of phi Xv, phi Xo and phi Lf were able to transfect X. c. pv. vesicatoria, X. o. pv. oryzae and X. c. pv. campestris. Physical maps of phi Xv and phi Xo were constructed for the RF DNAs. Genome sizes were estimated, based on mapping data, to be 6.8 kb for phi Xv and 7.6 kb for phi Xo, larger than that of the phi Lf genome (6.0 kb). The difference in genome sizes appeared to result from insertions of large DNA fragments. These fragments and the regions mediating integration were localized in the physical maps.
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Affiliation(s)
- N T Lin
- Department of Botany, National Chung Hsing University, Taichung, Taiwan, Republic of China
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Borek E, Baliga BS, Gehrke CW, Kuo CW, Belman S, Troll W, Waalkes TP. High turnover rate of transfer RNA in tumor tissue. Cancer Res 1977; 37:3362-6. [PMID: 884680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Cancer patients and tumor-bearing animals excrete high levels of modified purines and pyrimidines some of which, e.g., N2,N2-dimethylguanosine, can originate only from transfer RNA (tRNA). Until recently, it could not be ascertained whether the high level of excretion of such compounds is due to cell death or specific tRNA turnover. However, an approach to this problem became feasible, with beta-aminoisobutyric acid as a probe. This compound is a terminal degradation product of thymine which is present in both DNA and tRNA. Since the pathway of synthesis of thymine is different in the two macromolecules, it and its end product, beta-aminoisobutyric acid can be differentially labeled with [14C]formate and [3H3]methylmethionine as precursors. Therefore the ratio of the two labels in the excreted beta-aminoisobutyric acid is a measure of the macromolecular origin of the degradation product. We have found from such analysis that tRNA's are not homogeneous in their turnover rate. There is a subpopulation that turns over much faster than the rest. The turnover rate of a subpopulation of tRNA's in tumor tissue exceeds the turnover rate of tRNA's in normal tissue. Such rapid degradation of tRNA's must be the source of the massive excretion of modified nucleosides by cancer patients which can be 10-fold higher than in normal subjects.
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