95 results on '"Ranatunga, A."'
Search Results
2. Age-Dependent Regulation of Dendritic Spine Density and Protein Expression in Mir324 KO Mice
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Parkins, Emma V., primary, Burwinkel, John M., additional, Ranatunga, Ruvi, additional, Yaser, Sarah, additional, Hu, Yueh-Chiang, additional, Tiwari, Durgesh, additional, and Gross, Christina, additional
- Published
- 2023
- Full Text
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3. High Asymptomatic Cases of Babesiosis in Dogs and Comparison of Diagnostic Performance of Conventional PCR vs Blood Smears
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R. A. S. Ranatunga, A. Dangolla, S. D. S. S. Sooriyapathirana, and R. S. Rajakaruna
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Parasitology - Published
- 2022
4. A Re-evaluation of the Free Energy Profiles for Cell-Penetrating Peptides Across DOPC Membranes
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P. V. G. M. Rathnayake, B. T. Kumara, N. K. Wijesiri, and R. J. K. U. Ranatunga
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Chemistry ,Bilayer ,Bioengineering ,Sequence (biology) ,Biochemistry ,Analytical Chemistry ,Transduction (biophysics) ,Molecular dynamics ,Membrane ,Drug Discovery ,Amphiphile ,Biophysics ,Molecular Medicine ,Cytotoxicity ,Lipid bilayer - Abstract
Cell penetrating peptides (CPPs) hold immense potential for the transport of therapeutic agents to their active targets, due to their low cytotoxicity and high transduction efficiency. Adoption of CPPs as delivery systems, and development of novel peptides has been hampered by the variety of mechanisms and complexity of factors involved in cellular uptake. Quantitatively analyzing these systems is further hindered by the inability to compare data among reports due to varying experimental conditions. In this study we investigate the translocation of seventeen CPPs, representing cationic, amphipathic and hydrophobic physicochemical classes, through a DOPC membrane using molecular dynamics simulations. Free energy profiles for individual peptides inserting into the lipid bilayer were generated giving insight into both the approach and adsorption of different CPPs to cell membranes, and the feasibility of their direct translocation. The control of physical conditions and composition allows objective comparison of different peptides and analyze the effect of sequence on the adsorption and translocation energetics. Our results indicate that positively charged residues impart repulsion, while hydrophobic residues increase bilayer interaction. This study is the first step in fully understanding the processes and energetics involved in the passive translocation mechanisms of CPPs, which usually involve multiple peptides.
- Published
- 2021
5. Exposure Assessment of Fluoride Intake Through Commercially Available Black Tea (Camellia sinensis L.) from Areas with High Incidences of Chronic Kidney Disease with Undetermined Origin (CKDu) in Sri Lanka
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Johannes A. C. Barth, Sachini Bhagya, Mahasen A.B. Ranatunga, Saranga Diyabalanage, Rohana Chandrajith, and Swarna Wimalasiri
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Endocrinology, Diabetes and Metabolism ,Clinical Biochemistry ,Population ,010501 environmental sciences ,01 natural sciences ,Biochemistry ,Camellia sinensis ,Inorganic Chemistry ,Toxicology ,Fluorides ,03 medical and health sciences ,chemistry.chemical_compound ,Skeletal fluorosis ,medicine ,Humans ,Renal Insufficiency, Chronic ,education ,Sri Lanka ,0105 earth and related environmental sciences ,Exposure assessment ,0303 health sciences ,education.field_of_study ,Tea ,business.industry ,Incidence ,030302 biochemistry & molecular biology ,Biochemistry (medical) ,food and beverages ,General Medicine ,medicine.disease ,chemistry ,Sri lanka ,business ,Fluoride ,Dental fluorosis ,Kidney disease - Abstract
Fluoride is a beneficial trace element for human health as its deficiency and excess levels can cause detrimental health effects. In Sri Lanka, dry zone regions can have excessive levels of fluoride in drinking water and can cause dental and skeletal fluorosis. In addition to drinking water, traditional habits of tea consumption can cause an additional intake of fluoride in the population. A total number of 39 locally blended black tea samples were collected from a village where chronic kidney disease with undetermined origin (CKDu) is prevalent. In addition, unblended tea samples were obtained from tea-producing factories. The fluoride contents in infusions of 2% weight per volume (w/v) were measured using calibrated ion-selective fluoride electrodes. The mean fluoride content was 2.68±1.03 mg/L in loose tea, 1.87±0.57mg/L in packed tea samples, and 1.14±0.55 mg/L in unblended tea. Repeated brewing of the same tea leaves showed that over 50% of fluoride leached into the solution in the first infusion. An estimate of the daily total average fluoride intake via tea consumption per person is 2.68 mg per day. With groundwater in many dry zone regions in Sri Lanka showing high fluoride levels that exceed 0.5 mg/L, the additional daily intake can rapidly exceed recommended thresholds of 2 mg/day. This can add to adverse health impacts that might also relate to CKDu.
- Published
- 2021
6. High Asymptomatic Cases of Babesiosis in Dogs and Comparison of Diagnostic Performance of Conventional PCR vs Blood Smears
- Author
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Ranatunga, R. A. S., primary, Dangolla, A., additional, Sooriyapathirana, S. D. S. S., additional, and Rajakaruna, R. S., additional
- Published
- 2022
- Full Text
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7. UACA locus is associated with breast cancer chemoresistance and survival
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Zhu, Qianqian, primary, Schultz, Emily, additional, Long, Jirong, additional, Roh, Janise M., additional, Valice, Emily, additional, Laurent, Cecile A., additional, Radimer, Kelly H., additional, Yan, Li, additional, Ergas, Isaac J., additional, Davis, Warren, additional, Ranatunga, Dilrini, additional, Gandhi, Shipra, additional, Kwan, Marilyn L., additional, Bao, Ping-Ping, additional, Zheng, Wei, additional, Shu, Xiao-Ou, additional, Ambrosone, Christine, additional, Yao, Song, additional, and Kushi, Lawrence H., additional
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- 2022
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8. STABILISE; treatment of aortic dissection, a single Centre experience
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Goran Mitreski, Damian Flanders, Julian Maingard, Domenic Robinson, Jason Chuen, George Matalanis, Siven Seevanayagam, Hong Kuan Kok, Dinesh Ranatunga, Hamed Asadi, and Duncan Mark Brooks
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RC666-701 ,Diseases of the circulatory (Cardiovascular) system ,Original Article ,Radiology, Nuclear Medicine and imaging ,Cardiology and Cardiovascular Medicine - Abstract
Purpose To outline the process of the STABILISE technique and its use; reporting patient outcomes and midterm follow up for complicated aortic dissection. Materials and methods Single centre retrospective analysis from January 2011 to January 2021 using the STABILISE technique which utilises balloon assistance to facilitate intimal disruption and promote aortic relamination. Results Sixteen patients underwent endovascular aortic repair with the STABILISE technique for aortic dissection over the study period. Fourteen patients (14/16; 88%) had acute dissection. Two of 16 (12%) were chronic. The median age of the patient cohort was 61 years (range 32–80 years) and consisted of a male majority (n = 11; 69%). The median time from diagnosis to intervention was 5 days (1–115 days; IQR 1–17.3). More than half (56%) had surgical repair of a acute type A aortic dissection prior to radiological intervention. The procedure was technically successful with no procedural mortality. Two patients were lost to follow up and two died in the post-operative period. Twelve patients had ongoing follow up with an average number of 2.9 ± 1.6 scans performed. Follow up was available in thirteen patients (81%) with a median follow up period of 1097 days (IQR 707–1657). The rate of re-intervention (n = 2/16; 13%) requiring additional stenting was in line with published re-intervention data (15%). Follow up showed a reduction in false lumen size following treatment with total luminal dimensions remaining stable over the follow-up period. Conclusion The STABILISE technique as a procedure for complicated aortic dissection, either acute or chronic, appears safe with stable mid-term aortic remodelling and patient outcomes. Level of evidence Level 3, Retrospective cohort study.
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- 2022
9. STABILISE; treatment of aortic dissection, a single Centre experience
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Mitreski, Goran, primary, Flanders, Damian, additional, Maingard, Julian, additional, Robinson, Domenic, additional, Chuen, Jason, additional, Matalanis, George, additional, Seevanayagam, Siven, additional, Kok, Hong Kuan, additional, Ranatunga, Dinesh, additional, Asadi, Hamed, additional, and Brooks, Duncan Mark, additional
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- 2022
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10. A systematic review investigating patient knowledge and awareness on the association between oral health and their systemic condition
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Akl, Sabrina, primary, Ranatunga, Madusha, additional, Long, Sharron, additional, Jennings, Ernest, additional, and Nimmo, Alan, additional
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- 2021
- Full Text
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11. A Re-evaluation of the Free Energy Profiles for Cell-Penetrating Peptides Across DOPC Membranes
- Author
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Kumara, B. T., primary, Wijesiri, N. K., additional, Rathnayake, P. V. G. M., additional, and Ranatunga, R. J. K. U., additional
- Published
- 2021
- Full Text
- View/download PDF
12. Dr Gerald W. Offer (1938–2019); an appreciation
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Pauline M. Bennett, K. W. Ranatunga, and Peter J. Knight
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Physiology ,Chemistry ,Cell Biology ,Biochemistry ,Classics - Published
- 2019
13. Endovascular balloon-assisted liquid embolisation of soft tissue vascular malformations: technical feasibility and safety
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Lamanna, Anthony, primary, Maingard, Julian, additional, Florescu, Grace, additional, Kok, Hong Kuan, additional, Ranatunga, Dinesh, additional, Barras, Christen, additional, Lee, Michael J., additional, Brooks, Duncan Mark, additional, Jhamb, Ashu, additional, Chandra, Ronil V., additional, and Asadi, Hamed, additional
- Published
- 2021
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14. Exposure Assessment of Fluoride Intake Through Commercially Available Black Tea (Camellia sinensis L.) from Areas with High Incidences of Chronic Kidney Disease with Undetermined Origin (CKDu) in Sri Lanka
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Chandrajith, Rohana, primary, Bhagya, Sachini, additional, Diyabalanage, Saranga, additional, Wimalasiri, Swarna, additional, Ranatunga, Mahasen A.B., additional, and Barth, Johannes A. C., additional
- Published
- 2021
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15. Biochemical diversity of global tea [Camellia sinensis (L.) O. Kuntze] germplasm and its exploitation: a review
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M. T. Kumudini Gunasekare, J. Dananjaya Kottawa-Arachchi, and M. A. B. Ranatunga
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0106 biological sciences ,0301 basic medicine ,Germplasm ,Genetic diversity ,Abiotic stress ,fungi ,food and beverages ,Plant physiology ,Plant Science ,Biology ,complex mixtures ,01 natural sciences ,03 medical and health sciences ,030104 developmental biology ,Polyphenol ,Botany ,Genetics ,medicine ,Camellia sinensis ,Cultivar ,Agronomy and Crop Science ,Theobromine ,Ecology, Evolution, Behavior and Systematics ,010606 plant biology & botany ,medicine.drug - Abstract
Tea (Camellia sinensis L.) is the most widely-consumed beverage in the world. The biochemical components of tea leave include polyphenols (catechins and flavonoides), alkaloids (caffeine, theobromine, theophylline, etc.), volatile compounds, polysaccharides, amino acids, lipids and vitamins show a variety of bioactivities. Prolong cross-pollination nature of tea plants have produced considerable heritable variation, resulting in a high level of genetic diversity. The collection and conservation of the cultivars, landraces and wild relatives of the tea plant provides breeders with fundamental materials from which new cultivars are to be developed. The major role of tea breeding is to improve productivity, enhance tolerant to biotic and abiotic stress, and increase tea flavor and quality. Dissection of the genetic basis of these traits provides the potential for accelerating the breeding process by developing new tools such as marker-assisted selection. Therefore present review provides an overview of the biochemical and metabolite diversity of the global tea germplasm and its characterization and utilization.
- Published
- 2018
16. A large electronic-health-record-based genome-wide study of serum lipids
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Thomas J. Hoffmann, Elizabeth Theusch, Pui-Yan Kwok, Neil Risch, Carlos Iribarren, Dilrini K. Ranatunga, Marisa W. Medina, Ronald M. Krauss, Eric Jorgenson, Mark N. Kvale, Catherine Schaefer, and Tanushree Haldar
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Adult ,Male ,0301 basic medicine ,Genetic Linkage ,Quantitative Trait Loci ,Blood lipids ,Genome-wide association study ,Single-nucleotide polymorphism ,Biology ,liver ,Polymorphism, Single Nucleotide ,Article ,Linkage Disequilibrium ,statins ,Cohort Studies ,03 medical and health sciences ,chemistry.chemical_compound ,Gene Frequency ,HDL cholesterol ,Databases, Genetic ,Ethnicity ,Genetics ,Electronic Health Records ,Humans ,SNP ,Serum lipids ,pancreas ,Longitudinal Studies ,triglycerides ,Aged ,Genetic association ,genome-wide association study ,Triglyceride ,Cholesterol ,total cholesterol ,Middle Aged ,Lipid Metabolism ,Explained variation ,Lipids ,3. Good health ,030104 developmental biology ,chemistry ,LDL cholesterol ,Female ,lipids (amino acids, peptides, and proteins) ,Demography - Abstract
A genome-wide association study (GWAS) of 94,674 ancestrally diverse Kaiser Permanente members using 478,866 longitudinal electronic health record (EHR)-derived measurements for untreated serum lipid levels empowered multiple new findings: 121 new SNP associations (46 primary, 15 conditional, and 60 in meta-analysis with Global Lipids Genetic Consortium data); an increase of 33–42% in variance explained with multiple measurements; sex differences in genetic impact (greater impact in females for LDL, HDL, and total cholesterol and the opposite for triglycerides); differences in variance explained among non-Hispanic whites, Latinos, African Americans, and East Asians; genetic dominance and epistatic interaction, with strong evidence for both at the ABO and FUT2 genes for LDL; and tissue-specific enrichment of GWAS-associated SNPs among liver, adipose, and pancreas eQTLs. Using EHR pharmacy data, both LDL and triglyceride genetic risk scores (477 SNPs) were strongly predictive of age at initiation of lipid-lowering treatment. These findings highlight the value of longitudinal EHRs for identifying new genetic features of cholesterol and lipoprotein metabolism with implications for lipid treatment and risk of coronary heart disease. Genome-wide association analysis using electronic health record data from >94,000 individuals identifies loci associated with plasma lipid concentrations. Longitudinal measurements allow for the calculation of genetic risk scores and increase the variance explained.
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- 2018
17. Proportion of unplanned pregnancies, their determinants and health outcomes of women delivering at a teaching hospital in Sri Lanka
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Ranatunga, Iddamalgoda Dissanayakage Jayani Ch, primary and Jayaratne, Kapila, additional
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- 2020
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18. Endovascular flow-diversion of visceral and renal artery aneurysms using dual-layer braided nitinol carotid stents
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van Veenendaal, Penelope, primary, Maingard, Julian, additional, Kok, Hong Kuan, additional, Ranatunga, Dinesh, additional, Buckenham, Tim, additional, Chandra, Ronil V., additional, Lee, Michael J., additional, Brooks, Duncan Mark, additional, and Asadi, Hamed, additional
- Published
- 2020
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19. The impact of adjusting for baseline in pharmacogenomic genome-wide association studies of quantitative change
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Oni-Orisan, Akinyemi, primary, Haldar, Tanushree, additional, Ranatunga, Dilrini K., additional, Medina, Marisa W., additional, Schaefer, Catherine, additional, Krauss, Ronald M., additional, Iribarren, Carlos, additional, Risch, Neil, additional, and Hoffmann, Thomas J., additional
- Published
- 2020
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20. Endovascular treatment of visceral artery and renal aneurysms (VRAA) using a constant mesh density flow diverting stent
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Julian Maingard, Michael J. Lee, Anthony Lamanna, Rajeev Ravi, Hamed Asadi, Duncan Mark Brooks, Ronil V. Chandra, Hong Kuan Kok, and Dinesh Ranatunga
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Surpass ,lcsh:Diseases of the circulatory (Cardiovascular) system ,medicine.medical_specialty ,medicine.medical_treatment ,Case Report ,030204 cardiovascular system & hematology ,030218 nuclear medicine & medical imaging ,Gastroduodenal artery ,03 medical and health sciences ,0302 clinical medicine ,Aneurysm ,Renal artery ,medicine.artery ,Occlusion ,Visceral artery ,Medicine ,Radiology, Nuclear Medicine and imaging ,cardiovascular diseases ,Endovascular ,medicine.diagnostic_test ,business.industry ,Stent ,Hepatic artery ,Interventional radiology ,medicine.disease ,Neurovascular bundle ,medicine.anatomical_structure ,lcsh:RC666-701 ,Radiology ,Cardiology and Cardiovascular Medicine ,business ,Flow diverting stent ,Artery - Abstract
Background Flow diverting stents have been used safely and effectively for the treatment of intracranial aneurysms, particularly for large and wide necked aneurysms that are not amenable to conventional endovascular treatment with coiling. The Surpass Streamline device (Stryker Neurovascular, MI, USA) is a relatively new and unique flow diverting stent which maintains constant device mesh density over varying vessel diameters. This may potentially provide advantages compared to other flow diverting stents in achieving aneurysmal occlusion. Case presentation Two patients with VRAA were treated using the Surpass Streamline device. The first patient was a 65-year-old male with an incidental 2.4 cm aneurysm originating from the hepatic artery near the gastroduodenal artery (GDA). The second patient was a 56-year-old male with an incidental 1.9 cm renal aneurysm arising from an anterior inferior segmental branch of the left renal artery. A Surpass flow diverting stent was used to successfully exclude the aneurysm neck in both cases. Reduced flow was achieved in one patient (equivalent to O’Kelly-Marotta [OKM] Grade B1). Preserved flow and stagnation (equivalent to OKM Grade A3) was achieved in the other. There was preserved distal flow in the parent arteries. No immediate complications were encountered in either case. Complete occlusion of both aneurysms was seen on follow up CT angiographic imaging within 8-weeks. Conclusions The Surpass flow diverting stent can be used safely and effectively to treat VRAA. It should be considered in unruptured large and giant wide necked VRAAs aneurysms. Additional large prospective studies are required for further validation.
- Published
- 2019
21. Human–Robot Gesture Analysis for Objective Assessment of Autism Spectrum Disorder
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Nicoleta L. Bugnariu, Dan O. Popa, Namrata Balakrishnan, Indika B. Wijayasinghe, and Isura Ranatunga
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Dynamic time warping ,General Computer Science ,Social Psychology ,media_common.quotation_subject ,Speech recognition ,05 social sciences ,medicine.disease ,Motion capture ,050105 experimental psychology ,Developmental psychology ,Robot control ,Human-Computer Interaction ,Philosophy ,Control and Systems Engineering ,Autism spectrum disorder ,medicine ,Autism ,0501 psychology and cognitive sciences ,Electrical and Electronic Engineering ,Imitation ,Psychology ,050107 human factors ,Humanoid robot ,media_common ,Gesture - Abstract
In this paper we study the use of human robot interaction as a mean to objectively evaluate imitation deficits in children with autism. Robot control and data analysis methods were combined to assess the quality of interaction between the robot and the subjects. Humanoid robot Zeno was used to execute upper body gestures which the subjects were asked to imitate. The resulting motion of the subject was acquired through a motion capture system and compared with the intended motion performed by Zeno using the dynamic time warping (DTW) algorithm. During this study, the clinical hypothesis was that the resulting DTW cost can serve as a quantitative measure for the similarity between the motions, and thus can be used to objectively assess the severity of imitation deficits exhibited by the child. To validate this hypothesis, we present two sets of experiments, one with a set of healthy adults and the other with a group of children, some with autism spectrum disorder. The experiment with adult subjects serves as a statistically significant test to demonstrate the viability of the DTW cost as a similarity measure for the gesture analysis, whereas the experiment with child subjects is a pilot study to differentiate imitation performance for children with autism.
- Published
- 2016
22. Model reference adaptive impedance control for physical human-robot interaction
- Author
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Frank L. Lewis, Bakur AlQaudi, Isura Ranatunga, Shaikh M. Tousif, Dan O. Popa, and Hamidreza Modares
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0209 industrial biotechnology ,Engineering ,Control and Optimization ,Adaptive control ,business.industry ,Aerospace Engineering ,Control engineering ,02 engineering and technology ,Human–robot interaction ,Task (project management) ,020901 industrial engineering & automation ,Impedance control ,Control and Systems Engineering ,Control theory ,0202 electrical engineering, electronic engineering, information engineering ,Trajectory ,Robot ,020201 artificial intelligence & image processing ,business ,Inner loop - Abstract
This paper presents a novel enhanced human-robot interaction system based on model reference adaptive control. The presented method delivers guaranteed stability and task performance and has two control loops. A robot-specific inner loop, which is a neuroadaptive controller, learns the robot dynamics online and makes the robot respond like a prescribed impedance model. This loop uses no task information, including no prescribed trajectory. A task-specific outer loop takes into account the human operator dynamics and adapts the prescribed robot impedance model so that the combined human-robot system has desirable characteristics for task performance. This design is based on model reference adaptive control, but of a nonstandard form. The net result is a controller with both adaptive impedance characteristics and assistive inputs that augment the human operator to provide improved task performance of the human-robot team. Simulations verify the performance of the proposed controller in a repetitive point-to-point motion task. Actual experimental implementations on a PR2 robot further corroborate the effectiveness of the approach.
- Published
- 2016
23. Dr Gerald W. Offer (1938–2019); an appreciation
- Author
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Bennett, Pauline, primary, Knight, Peter J., additional, and Ranatunga, K. W., additional
- Published
- 2019
- Full Text
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24. Endovascular treatment of visceral artery and renal aneurysms (VRAA) using a constant mesh density flow diverting stent
- Author
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Maingard, Julian, primary, Lamanna, Anthony, additional, Kok, Hong Kuan, additional, Ranatunga, Dinesh, additional, Ravi, Rajeev, additional, Chandra, Ronil V., additional, Lee, Michael J., additional, Brooks, Duncan Mark, additional, and Asadi, Hamed, additional
- Published
- 2019
- Full Text
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25. Combined Vertebral Augmentation and Radiofrequency Ablation in the Management of Spinal Metastases: an Update
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William C. Torreggiani, Ning Mao Kam, Hong Kuan Kok, Duncan Mark Brooks, Michael J. Lee, Ronil V. Chandra, Julian Maingard, Hamed Asadi, Peter L. Munk, and Dinesh Ranatunga
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medicine.medical_specialty ,Percutaneous ,Radiofrequency ablation ,medicine.medical_treatment ,030218 nuclear medicine & medical imaging ,Metastasis ,law.invention ,Percutaneous vertebroplasty ,03 medical and health sciences ,0302 clinical medicine ,law ,Neoplasms ,Humans ,Minimally Invasive Surgical Procedures ,Medicine ,Pharmacology (medical) ,Vertebroplasty ,Spinal Neoplasms ,medicine.diagnostic_test ,business.industry ,Soft tissue ,Cancer ,Interventional radiology ,medicine.disease ,Combined Modality Therapy ,Surgery ,Radiation therapy ,Treatment Outcome ,Oncology ,Catheter Ablation ,Quality of Life ,Spinal Fractures ,Radiology ,business ,030217 neurology & neurosurgery - Abstract
Spinal metastases are the most commonly encountered tumour of the spine, occurring in up to 40% of patients with cancer. Each year, approximately 5% of cancer patients will develop spinal metastases. This number is expected to increase as the life expectancy of cancer patients increases. Patients with spinal metastases experience severe and frequently debilitating pain, which often decreases their remaining quality of life. With a median survival of less than 1 year, the goals of treatment in spinal metastases are reducing pain, improving or maintaining level of function and providing mechanical stability. Currently, conventional treatment strategies involve a combination of analgesics, bisphosphonates, radiotherapy and/or relatively extensive surgery. Despite these measures, pain management in patients with spinal metastases is often suboptimal. In the last two decades, minimally invasive percutaneous interventional radiology techniques such as vertebral augmentation and radiofrequency ablation (RFA) have shown progressive success in reducing pain and improving function in many patients with symptomatic spinal metastases. Both vertebral augmentation and RFA are increasingly being recognised as excellent alternative to medical and surgical management in carefully selected patients with spinal metastases, namely those with severe refractory pain limiting daily activities and stable pathological vertebral compression fractures. In addition, for more complicated lesions such as spinal metastasis with soft tissue extension, combined treatments such as vertebral augmentation in conjunction with RFA may be helpful. While combined RFA and vertebral augmentation have theoretical benefits, comparative trials have not been performed to establish superiority of combined therapy. We believe that a multidisciplinary approach as well as careful pre-procedure evaluation and imaging will be necessary for effective and safe management of spinal metastases. RFA and vertebral augmentation should be considered during early stages of the disease so as to maintain the remaining quality of life in this patient population group.
- Published
- 2017
26. Genome-wide association study of prostate-specific antigen levels identifies novel loci independent of prostate cancer
- Author
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Rebecca E. Graff, Chun Chao, Neil Risch, Laurel A. Habel, John S. Witte, Pui-Yan Kwok, Sonja I. Berndt, Olle Melander, Mark N. Kvale, Stephen J. Chanock, Lori C. Sakoda, Nima C. Emami, Michael N. Passarelli, Stephen K. Van Den Eeden, Thomas J. Hoffmann, Eric Jorgenson, Hans Lilja, Joseph C. Presti, Zhaoming Wang, Catherine Schaefer, Dilrini K. Ranatunga, Jonathan D. Mosley, David S. Aaronson, Jun Shan, Robert J. Klein, Nirupa R. Ghai, Mridu Middha, Charles P. Quesenberry, and Tobias Nordström
- Subjects
Adult ,Male ,0301 basic medicine ,medicine.medical_specialty ,Science ,Black People ,Gene Expression ,General Physics and Astronomy ,Single-nucleotide polymorphism ,Genome-wide association study ,urologic and male genital diseases ,Bioinformatics ,Polymorphism, Single Nucleotide ,White People ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,Prostate cancer ,Asian People ,Gene Frequency ,Antigen ,Biomarkers, Tumor ,medicine ,Humans ,Alleles ,Aged ,Aged, 80 and over ,Multidisciplinary ,business.industry ,Prostate ,Prostatic Neoplasms ,General Chemistry ,Middle Aged ,Prostate-Specific Antigen ,medicine.disease ,3. Good health ,Prostate-specific antigen ,030104 developmental biology ,Genetic Loci ,Genetic marker ,Medical genetics ,business ,Genome-Wide Association Study - Abstract
Prostate-specific antigen (PSA) levels have been used for detection and surveillance of prostate cancer (PCa). However, factors other than PCa—such as genetics—can impact PSA. Here we present findings from a genome-wide association study (GWAS) of PSA in 28,503 Kaiser Permanente whites and 17,428 men from replication cohorts. We detect 40 genome-wide significant (P−8) single-nucleotide polymorphisms (SNPs): 19 novel, 15 previously identified for PSA (14 of which were also PCa-associated), and 6 previously identified for PCa only. Further analysis incorporating PCa cases suggests that at least half of the 40 SNPs are PSA-associated independent of PCa. The 40 SNPs explain 9.5% of PSA variation in non-Hispanic whites, and the remaining GWAS SNPs explain an additional 31.7%; this percentage is higher in younger men, supporting the genetic basis of PSA levels. These findings provide important information about genetic markers for PSA that may improve PCa screening, thereby reducing over-diagnosis and over-treatment.
- Published
- 2017
27. Liver adenomatosis: serial investigation on MRI
- Author
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Wirana Angthong, Bong Soo Kim, Paul H. Hayashi, Saowanee Srirattanapong, Richard C. Semelka, Jared Peacock, David A. Gerber, John T. Woosley, and Anuruddika Ranatunga
- Subjects
Adenoma ,Adult ,Gadolinium DTPA ,Male ,medicine.medical_specialty ,Adolescent ,Urology ,Remission, Spontaneous ,Contrast Media ,Gastroenterology ,Malignant transformation ,Benign tumor ,Lesion ,Meglumine ,Stable Disease ,Internal medicine ,Organometallic Compounds ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Retrospective Studies ,Radiological and Ultrasound Technology ,business.industry ,Liver Neoplasms ,General Medicine ,Middle Aged ,Hepatology ,Hepatocellular adenoma ,medicine.disease ,Magnetic Resonance Imaging ,Natural history ,Clinical diagnosis ,Disease Progression ,Female ,Radiology ,medicine.symptom ,business - Abstract
To describe the natural history of liver adenomatosis (LA), including complications and changes in lesion size over time. Eighteen patients with clinical diagnosis of LA were included. Clinical and biochemical information were collected. The initial and follow-up MR studies were reviewed retrospectively to determine change in lesion size and imaging features. Seventeen patients were women (94.4%). The mean age of the initial MR study was 37.0 years (18–52 years). The median size of the largest lesion was 6.7 cm (range 3.0–13.5 cm). Intratumoral bleeding was detected on MRI in 9 lesions, in 7 patients (38.8%). The median size for hemorrhagic lesions was 7.6 cm (range 4.1–13.5 cm). During the mean follow-up period of 29.4 (range 4–98) months, 10 patients had stable disease (55.6%), and 8 patients had tumor regression (44.4%). Of 8 patients who were followed without intervention, 3 patients (37.5%) had spontaneous regression. No malignant transformation or lesion progression was occurred. During an over 2-year follow-up period, the majority of lesions of LA appeared to remain stable or showed tumor regression. Spontaneous tumor regression can be observed in approximately 37% of individuals in the age range of 28–53 years.
- Published
- 2013
28. Mechanotransduction is required for establishing and maintaining mature inner hair cells and regulating efferent innervation
- Author
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Corns, Laura F., primary, Johnson, Stuart L., additional, Roberts, Terri, additional, Ranatunga, Kishani M., additional, Hendry, Aenea, additional, Ceriani, Federico, additional, Safieddine, Saaid, additional, Steel, Karen P., additional, Forge, Andy, additional, Petit, Christine, additional, Furness, David N., additional, Kros, Corné J., additional, and Marcotti, Walter, additional
- Published
- 2018
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29. Biochemical diversity of global tea [Camellia sinensis (L.) O. Kuntze] germplasm and its exploitation: a review
- Author
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Kottawa-Arachchi, J. Dananjaya, primary, Gunasekare, M. T. Kumudini, additional, and Ranatunga, Mahasen A. B., additional
- Published
- 2018
- Full Text
- View/download PDF
30. A large electronic-health-record-based genome-wide study of serum lipids
- Author
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Hoffmann, Thomas J., primary, Theusch, Elizabeth, additional, Haldar, Tanushree, additional, Ranatunga, Dilrini K., additional, Jorgenson, Eric, additional, Medina, Marisa W., additional, Kvale, Mark N., additional, Kwok, Pui-Yan, additional, Schaefer, Catherine, additional, Krauss, Ronald M., additional, Iribarren, Carlos, additional, and Risch, Neil, additional
- Published
- 2018
- Full Text
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31. Combined Vertebral Augmentation and Radiofrequency Ablation in the Management of Spinal Metastases: an Update
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Kam, Ning Mao, primary, Maingard, Julian, additional, Kok, Hong Kuan, additional, Ranatunga, Dinesh, additional, Brooks, Duncan, additional, Torreggiani, William C., additional, Munk, Peter L., additional, Lee, Michael J., additional, Chandra, Ronil V., additional, and Asadi, Hamed, additional
- Published
- 2017
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32. Mechanism of force enhancement during and after lengthening of active muscle: a temperature dependence study
- Author
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KW Ranatunga, Gavin J. Pinniger, H Roots, and Gerald Offer
- Subjects
Male ,Sarcomeres ,Physiology ,Isometric exercise ,Models, Biological ,Biochemistry ,Sarcomere ,CrossBridge ,Isometric Contraction ,Muscle tension ,medicine ,Animals ,Muscle Strength ,Tension (physics) ,Chemistry ,Temperature ,Cell Biology ,Anatomy ,Atmospheric temperature range ,Rats ,Muscle Tonus ,Muscle Fibers, Fast-Twitch ,Biophysics ,Active muscle ,Tetanic contraction ,medicine.symptom - Abstract
The aim of the present study was to examine the temperature dependence of active force in lengthening and shortening muscle. Experiments were done, in vitro, on bundles of intact fibres (fibre length L(0) ~2 mm; sarcomere length ~2.5 μm) isolated from a rat fast muscle (flexor hallucis brevis) and a ramp length change of 5-7% L(0) was applied on the plateau of an isometric tetanic contraction. Ramp lengthening increased and ramp shortening decreased the muscle tension to new approximately steady levels in a velocity-dependent way. The isometric tension and the lower steady tension reached at a given shortening velocity, increased with warming from 10 to 35 °C and the relation between tension and reciprocal absolute temperature was sigmoidal. However, the tension-temperature curve of shortening muscle was sharper and shifted to higher temperature with increased velocity. In contrast, the enhanced steady tension during lengthening at a given velocity was largely temperature-insensitive within the same temperature range; we hypothesize that the tension-temperature curve may be shifted to lower temperatures in lengthening muscle. Consequently, when normalised to the isometric tension at each temperature, the tension during lengthening at a given velocity decreased exponentially with increase of temperature. The residual force enhancement that remains after ramp lengthening showed a similar behaviour and was markedly reduced in warming from 10 to 35 °C. The findings are consistent with the thesis that active force generation in muscle is endothermic and strain-sensitive; during shortening with a faster crossbridge cycle it becomes more pronounced, but during lengthening it becomes depressed as the cycle slows in a velocity-dependent way. The residual force enhancement may be caused by the same process in addition to non-crossbridge mechanism(s).
- Published
- 2012
33. Crossbridge and filament compliance in muscle: implications for tension generation and lever arm swing
- Author
-
K. W. Ranatunga and Gerald Offer
- Subjects
Sarcomeres ,Ranidae ,Physiology ,Movement ,Edible frog ,macromolecular substances ,Isometric exercise ,Myosins ,Biochemistry ,Rana ,Protein filament ,Myosin head ,CrossBridge ,Isometric Contraction ,biology.animal ,Myosin ,Animals ,Muscle, Skeletal ,Cytoskeleton ,Actin ,biology ,Chemistry ,Muscles ,Cell Biology ,Anatomy ,Actins ,Elasticity ,Biomechanical Phenomena ,Models, Structural ,Actin Cytoskeleton ,Muscle Tonus ,Biophysics ,Thermodynamics ,Rabbits - Abstract
The stiffness of myosin heads attached to actin is a crucial parameter in determining the kinetics and mechanics of the crossbridge cycle. It has been claimed that the stiffness of myosin heads in the anterior tibialis muscle of the common frog (Rana temporaria) is as high as 3.3 pN/nm, substantially higher than its value in rabbit muscle (~1.7 pN/nm). However, the crossbridge stiffness measurement has a large error since the contribution of crossbridges to half-sarcomere compliance is obtained by subtracting from the half-sarcomere compliance the contributions of the thick and thin filaments, each with a substantial error. Calculation of its value for isometric contraction also depends on the fraction of heads that are attached, for which there is no consensus. Surprisingly, the stiffness of the myosin head from the edible frog, Rana esculenta, determined in the same manner, is only 60% of that in Rana temporaria. In our view it is unlikely that the value of such a crucial parameter could differ so substantially between two frog species. Since the means of the myosin head stiffness in these two species are not significantly different, we suggest that the best estimate of the stiffness of the myosin heads for frog muscle is the average of these data, a value similar to that for rabbit muscle. This would allow both frog and rabbit muscles to operate the same low-cooperativity mechanism for the crossbridge cycle with only one or two tension-generating steps. We review evidence that much of the compliance of the myosin head is located in the pliant region where the lever arm emerges from the converter and propose that tension generation ("tensing") caused by the rotation and movement of the converter is a separate event from the passive swinging of the lever arm in its working stroke in which the strain energy stored in the pliant region is used to do work.
- Published
- 2010
34. Migratory Polyarthritis as a Paraneoplastic Syndrome
- Author
-
Sriya K. M. Ranatunga, Jennifer Brenneman, Ani Annamalai, and Melanie Zupancic
- Subjects
Adult ,Male ,Pathology ,medicine.medical_specialty ,Lung Neoplasms ,Case Reports/Clinical Vignettes ,Paraneoplastic Syndromes ,business.industry ,Arthritis ,medicine.disease ,Malignancy ,Pathophysiology ,Bronchogenic carcinoma ,Diagnosis, Differential ,Inflammatory polyarthritis ,Migratory arthritis ,Internal Medicine ,medicine ,Humans ,Migratory polyarthritis ,Polyarthritis ,Differential diagnosis ,business - Abstract
Carcinomatous polyarthritis (CP) is a rare paraneoplastic disorder that has been associated with a variety of solid tumors. It presents in a similar manner to other polyarticular disorders and often precedes detection of the underlying malignancy, making recognition critical. CP responds to the treatment of the neoplastic process. We present a patient who initially presented with asymmetric inflammatory polyarthritis who was later diagnosed with bronchogenic carcinoma. Following the case report we present our learning objectives, which include the differential diagnosis of inflammatory polyarthritis, diagnostic approach to CP, and features that distinguish it from other more common causes of polyarthritis. We conclude with a brief discussion of the pathophysiology and management of CP.
- Published
- 2008
35. Stat4-dependent, T-bet-independent regulation of IL-10 in NK cells
- Author
-
Christian M. Hedrich, Wilson K, Fengying Wang, Lindsay R. Grant, Dilini Ranatunga, Yao Zj, Moorthy A, and Jay H. Bream
- Subjects
Time Factors ,Immunology ,Population ,Cell Culture Techniques ,Stimulation ,Article ,Interferon-gamma ,Mice ,Genetics ,Animals ,RNA, Messenger ,education ,Gene ,STAT4 ,Cells, Cultured ,Genetics (clinical) ,education.field_of_study ,biology ,Drug Synergism ,STAT4 Transcription Factor ,Interleukin-12 ,Stimulation, Chemical ,Interleukin-10 ,Cell biology ,Killer Cells, Natural ,Mice, Inbred C57BL ,Kinetics ,Interleukin 10 ,Histone ,Cell culture ,Interleukin 12 ,biology.protein ,Interleukin-2 ,T-Box Domain Proteins ,Spleen - Abstract
Interleukin-10 (IL-10) is intensely studied, yet little is known about the mechanisms that control IL-10 expression. We identified striking similarities between IL-10 and interferon-gamma (IFN-gamma) regulation in mouse natural killer (NK) cells. Like IFN-gamma, IL-10 expression is induced by IL-2 and IL-12 and IL-2+IL-12 stimulation is synergistic. Unlike IFN-gamma, neither IL-18 nor Ly-49D cross-linking induced IL-10 expression however. Additionally, the IL-12 homologs IL-23 and IL-27 also do not regulate NK cell-specific IL-10. We determined that a small population of NK cells accounts for IL-10 production. The induction of IL-10 by IL-2+IL-12 treatment in NK cells appears to be biphasic, with an initial burst of expression which diminishes by 12 h but spikes again at 18 h. We determined that much like IFN-gamma, Stat4 is largely required for IL-12-induced IL-10. Conversely, we observed normal induction of IL-10 in T-bet-deficient NK cells. We identified a Stat4-binding element in the fourth intron of the Il10 gene, which is completely conserved between mouse and human. This intronic Stat4 motif is within a conserved noncoding sequence, which is also a target for cytokine-induced histone acetylation. These findings highlight tissue- and receptor-specific IL-10 regulatory mechanisms, which may be part of an early feedback loop.
- Published
- 2008
36. Endovascular Treatment of Wide-Necked Visceral Artery Aneurysms Using the Neurovascular Comaneci Neck-Bridging Device: A Technical Report
- Author
-
Maingard, Julian, primary, Kok, Hong Kuan, additional, Phelan, Emma, additional, Logan, Caitriona, additional, Ranatunga, Dinesh, additional, Brooks, Duncan Mark, additional, Chandra, Ronil V., additional, Lee, Michael J., additional, and Asadi, Hamed, additional
- Published
- 2017
- Full Text
- View/download PDF
37. Genome-wide association study of prostate-specific antigen levels identifies novel loci independent of prostate cancer
- Author
-
Hoffmann, Thomas J., primary, Passarelli, Michael N., additional, Graff, Rebecca E., additional, Emami, Nima C., additional, Sakoda, Lori C., additional, Jorgenson, Eric, additional, Habel, Laurel A., additional, Shan, Jun, additional, Ranatunga, Dilrini K., additional, Quesenberry, Charles P., additional, Chao, Chun R., additional, Ghai, Nirupa R., additional, Aaronson, David, additional, Presti, Joseph, additional, Nordström, Tobias, additional, Wang, Zhaoming, additional, Berndt, Sonja I., additional, Chanock, Stephen J., additional, Mosley, Jonathan D., additional, Klein, Robert J., additional, Middha, Mridu, additional, Lilja, Hans, additional, Melander, Olle, additional, Kvale, Mark N., additional, Kwok, Pui-Yan, additional, Schaefer, Catherine, additional, Risch, Neil, additional, Van Den Eeden, Stephen K., additional, and Witte, John S., additional
- Published
- 2017
- Full Text
- View/download PDF
38. Giant Cell Arteritis Presenting as Small Bowel Infarction
- Author
-
Sriya K. M. Ranatunga, Aniyizhai Annamalai, David S. Resch, and Mark L. Francis
- Subjects
medicine.medical_specialty ,Systemic disease ,Case Reports/Clinical Vignettes ,Infarction ,small bowel infarction ,Blindness ,Fatal Outcome ,Intestine, Small ,Internal Medicine ,medicine ,Humans ,vasculitic disorders ,Aged ,Bowel infarction ,giant cell arteritis ,business.industry ,Vascular disease ,medicine.disease ,Mesenteric Arteries ,Surgery ,Bowel obstruction ,Giant cell arteritis ,temporal arteritis ,Female ,Differential diagnosis ,business ,Vasculitis ,Intestinal Obstruction - Abstract
Giant cell arteritis predominantly affects cranial arteries and rarely involves other sites. We report a patient who presented with small bowel obstruction because of infarction from mesenteric giant cell arteritis. She had an unusual cause of her obstruction and a rare manifestation of giant cell arteritis. In spite of aggressive therapy with steroids, she died a month later because of multiple complications. We discuss the diagnosis and management of small bowel obstruction and differential diagnosis of vasculitis of the gastrointestinal tract. We were able to find 11 cases of bowel involvement with giant cell arteritis in the English literature. This case report illustrates that giant cell arteritis can be a cause of small bowel obstruction and bowel infarction. In the proper clinical setting, vasculitides need to be considered early in the differential diagnosis when therapy may be most effective.
- Published
- 2007
39. Genome-wide association analyses using electronic health records identify new loci influencing blood pressure variation
- Author
-
Hoffmann, Thomas J, primary, Ehret, Georg B, additional, Nandakumar, Priyanka, additional, Ranatunga, Dilrini, additional, Schaefer, Catherine, additional, Kwok, Pui-Yan, additional, Iribarren, Carlos, additional, Chakravarti, Aravinda, additional, and Risch, Neil, additional
- Published
- 2016
- Full Text
- View/download PDF
40. A partial diallel study of powdery mildew resistance in six apple cultivars under three growing conditions with different disease pressures
- Author
-
Peter A. Alspach, Nnadozie Oraguzie, C. Whitworth, C. Ranatunga, and Vincent G. M. Bus
- Subjects
Podosphaera leucotricha ,Mildew ,biology ,Rosaceae ,food and beverages ,Plant Science ,Horticulture ,biology.organism_classification ,Major gene ,Diallel cross ,Botany ,Genetics ,Cultivar ,Agronomy and Crop Science ,Fruit tree ,Powdery mildew - Abstract
The suitability of large-fruited apple cultivars as alternative donors of powdery mildew resistance to the crabapples carrying major gene resistances was assessed. Five accessions with varying levels of mildew resistance (‘Dulmener Rosen', ‘Liberty', ‘Sciros', ‘Prima' and ‘Red Delicious') and one susceptible cultivar (‘Cox's Orange Pippin') were mated in a partial diallel design, and sub-sets of each seedling family were evaluated for three years at three New Zealand sites (Havelock North, Riwaka and Clyde) with different climatic conditions. There was a high correlation among the powdery mildew susceptibility scores of the individual seedlings over the three years, but disease levels varied among sites, with those at Clyde being the highest. All accessions with some resistance were found to confer additive resistance to their progenies to varying degrees depending on the climatic conditions of the sites, but findings suggest that progeny selection at Clyde will be sufficient for breeding purposes. The performance of the cultivar itself was not necessarily a good predictor of the level of resistance conferred to its progenies. The mostly negative genetic correlations between powdery mildew scores and fruit quality attributes suggest that selecting for powdery mildew resistance and desirable fruit quality traits may not be difficult. However, a larger number of families may be needed for more precise estimates of the genetic correlations to strengthen confidence in this conclusion.
- Published
- 2006
41. UBET-Based Numerical Modeling of Bulk Deformation Processes
- Author
-
Jay S. Gunasekera and Vipul Ranatunga
- Subjects
Materials science ,business.product_category ,Mechanical Engineering ,Design tool ,Process (computing) ,Mechanical engineering ,Deformation (meteorology) ,Upper and lower bounds ,Finite element method ,Forging ,Mechanics of Materials ,Die (manufacturing) ,General Materials Science ,Engineering design process ,business - Abstract
The paper summarizes the development of numerical procedures for modeling bulk deformation process and preform designing techniques based on the upper bound elemental technique (UBET). UBET has a unique place where an approximate, but faster solution is needed for decision making. In designing and optimizing multistage forging and profile ring-rolling processes, an approximate solution can be used to identify the most influential process parameters. Once an optimum combination of process conditions are determined, computationally intensive, but more accurate finite element analysis can be used to verify and refine results. In this paper, UBET procedures for closed-die forging and profile ring rolling are high-lighted. Experimental investigations are used to validate the model predictions. Also, the UBET-based preform design tool is presented as a process and die design tool for multistage forging processes. Application of these techniques is presented with evidence of effective material usage and extended overall die-life.
- Published
- 2006
42. Effects of a Myosin-II Inhibitor (N-benzyl-p-toluene Sulphonamide, BTS) on Contractile Characteristics of Intact Fast-twitch Mammalian Muscle Fibres
- Author
-
K. W. Ranatunga, Håkan Westerblad, Gavin J. Pinniger, and Joseph D. Bruton
- Subjects
Male ,Physiology ,Mammalian muscle ,Muscle Fibers, Skeletal ,In Vitro Techniques ,Biology ,Biochemistry ,chemistry.chemical_compound ,Isometric Contraction ,Myosin ,medicine ,Animals ,Potency ,Calcium Signaling ,Rats, Wistar ,Muscle, Skeletal ,Calcium signaling ,Myosin Type II ,Calcium metabolism ,Sulfonamides ,Dose-Response Relationship, Drug ,Temperature ,Cell Biology ,Anatomy ,Toluene ,Rats ,Dose–response relationship ,chemistry ,Muscle Fibers, Fast-Twitch ,Biophysics ,Calcium ,medicine.symptom ,Muscle Contraction ,Muscle contraction - Abstract
We have examined the effects of N-benzyl-p-toluene sulphonamide (BTS), a potent and specific inhibitor of fast muscle myosin-II, using small bundles of intact fibres or single fibres from rat foot muscle. BTS decreased tetanic tension reversibly in a concentration-dependent manner with half-maximal inhibition at approximately approximately 2 microM at 20 degrees C. The inhibition of tension with 10 microM BTS was marked at the three temperatures examined (10, 20 and 30 degrees C), but greatest at 10 degrees C. BTS decreased active muscle stiffness to a lesser extent than tetanic tension indicating that not all of the tension inhibition was due to a reduced number of attached cross-bridges. BTS-induced inhibition of active tension was not accompanied by any change in the free myoplasmic Ca2+ transients. The potency and specificity of BTS make it a very suitable myosin inhibitor for intact mammalian fast muscle and should be a useful tool for the examination of outstanding questions in muscle contraction.
- Published
- 2005
43. Tension Responses to Rapid (Laser) Temperature-jumps during Twitch Contractions in Intact Rat Muscle Fibres
- Author
-
M. E. Coupland, K. W. Ranatunga, and Gavin J. Pinniger
- Subjects
Male ,Physiology ,Muscle Fibers, Skeletal ,chemistry.chemical_element ,Stimulation ,In Vitro Techniques ,Calcium ,Biochemistry ,Sarcomere ,law.invention ,CrossBridge ,law ,medicine ,Animals ,Physiological saline ,Foot ,Chemistry ,Lasers ,Temperature ,Skeletal muscle ,Cell Biology ,Anatomy ,Laser ,Electric Stimulation ,Rats ,medicine.anatomical_structure ,Muscle Fibers, Fast-Twitch ,Biophysics ,Tetanic contraction ,Stress, Mechanical ,medicine.symptom ,Muscle Contraction - Abstract
We examined the tension responses induced by rapid temperature-jumps (T-jumps) applied at different times during twitch and tetanic contractions in small intact fibre bundles (5-10 fibres) isolated from a fast foot muscle (flexor hallucis brevis) of the rat. A rapid T-jump of 2-4 degrees C was induced by a 0.2 ms infrared (lambda = 1.32 microm) laser pulse applied to the fibre bundle immersed in a 50 microl trough of physiological saline, the temperature of which was clamped at different steady temperatures ranging from 10 to 30 degrees C. In a tetanic contraction, the tension increased to the same steady level when a standard T-jump was applied at different intervals after the onset of stimulation; thus, with maximal activation, an enhanced force generation by T-jump leads to a new steady state. In a twitch contraction, a T-jump induced a large, potentiation of tension when it was applied during the rising phase. Whereas the twitch relaxation subsequent to a T-jump was faster in all cases, the amplitude of the twitch tension potentiation decreased as the T-jump was delayed with respect to the stimulus, and there was no increase of tension when a T-jump was placed on the relaxation phase of the twitch. The increase of tension induced by a T-jump applied on the rising phase resulted in peak tension that was greater than the tension in control twitches at the steady post-T-jump temperature; therefore tension was higher than that expected on the basis of steady state temperature dependence of twitch tension. Whether these effects on a twitch contraction arise from differential fibre-heating by a T-jump that leads to shortening and development of sarcomere length disorder etc remain unclear. However, the findings may be interpreted as indicating that twitch tension increment by a T-jump occurs when excitation (the action potential) leading to calcium release and thin filament activation occur at the low temperature, whereas the crossbridge force-generation processes (and Ca2+-uptake) proceed at the higher temperature.
- Published
- 2005
44. [Untitled]
- Author
-
Nimali Ranatunga and Asiri Nanayakkara
- Subjects
Sequence ,Physics and Astronomy (miscellaneous) ,General Mathematics ,Quantization (signal processing) ,Mathematical analysis ,Schrödinger equation ,symbols.namesake ,symbols ,Limit of a sequence ,Limit (mathematics) ,Quantum ,Eigenvalues and eigenvectors ,Mathematics ,Analytic function - Abstract
A quantum dynamical equation is constructed as the limit of a sequence of functions (called Semiquantum momentum functions or SQMF). The quantum action variable J is defined as the limit of the sequence of contour integrals of SQMFs such that the quantization condition is J = nħ, where n is a nonnegative integer for eigenvalues and a noninteger for off eigenvalues. This quantization condition is exact and J is an analytic function of energy. Based on new definitions, an accurate numerical method is developed for obtaining eigenenergies. The method can be applied to both real and PT symmetric complex potentials. The validity and the accuracy of this new method is demonstrated with three illustrations.
- Published
- 2002
45. [Untitled]
- Author
-
K. W. Ranatunga
- Subjects
biology ,Physiology ,Chemistry ,Skeletal muscle ,Cell Biology ,Anatomy ,Biochemistry ,Sarcomere ,Protein filament ,Nebulin ,Myosin head ,medicine.anatomical_structure ,Myosin ,biology.protein ,medicine ,Biophysics ,Titin ,Elasticity (economics) - Abstract
The giant muscle protein titin (connectin), contained in the gap filament that connect a thick filament to the Z-line in a sarcomere, is generally considered to be responsible for the passive force (tension) and visco-elasticity in resting striated muscle. However, whether it can account for all the features of the resting tension response remains unclear. In this paper, we examine the basic features of the ‘sarcomeric visco-elasticity’ in a single resting mammalian muscle fibre and attempt to account for various tension components on the basis of known structural features of a sarcomere. At sarcomere length of ∼2.6 μm, the force response to a ramp stretch of 2–5% is complex but can be resolved into four functionally different components. The behaviour displayed by the components ranges from pure viscous type (directly proportional to stretch velocity, ranging from 0.1 to 30 lengths s−1) to predominantly elastic type (insensitive to stretch velocity at 1–2 s time scale); simulations show two components of visco-elasticity with characteristically different relaxation times. The velocity-sensitive components (only) are enhanced by filament lattice compression (dextran – 500 kD) and by increased medium viscosity (dextran – 12 kD); also, the relaxation time of visco-elasticity is longer with increased medium viscosity. Amplitude of all the components and the relaxation time of visco-elasticity are increased at longer sarcomere length (range ∼2.5 – 3.0 μm). The study, and quantitative analyses, extend our previous work on intact muscle fibres and suggest that the velocity-sensitive tension components in intact sarcomere arise from interactions between sarcomeric filaments, filament segments and inter-filamentary medium; the two components of visco-elasticity arise from distinct regions of titin (connectin) molecules.
- Published
- 2001
46. [Untitled]
- Author
-
Gabriel Mutungi and K. W. Ranatunga
- Subjects
Viscosity coefficient ,Break point ,Physiology ,Chemistry ,Tension response ,Biophysics ,Twitch tension ,Cell Biology ,Anatomy ,Muscle fibre ,Biochemistry ,Sarcomere ,Fibre type - Abstract
The effects of a ramp stretch (amplitude < 6% muscle fibre length (L0), speed < 13L0 s−1) on twitch tension and twitch tension re-development were examined in intact mammalian (rat) fast and slow muscle fibre bundles. The experiments were done in vitro at 20°C and at an initial sarcomere length of 2.68 μm. In both fibre types, a stretch applied during the rising phase of the twitch response (including the time of stimulation) increased the re-developed twitch tension (15–35%). A stretch applied before the stimulus had little or no effect on the twitch myogram in fast muscle fibres, but it increased the twitch tension (∼5%) in slow muscle fibres. A similar stretch had little or no effect on tetanic tension in either muscle fibre type. In general, the results indicate that the contractile-activation mechanism may be stretch sensitive and this is particularly pronounced in slow muscle fibres. Recorded at a high sampling rate and examined at an appropriate time scale, the transitory tension response to a stretch rose in at least two phases; an initial rapid tension rise to a break (break point tension, P1a) followed by a slower tension rise (apparent P2a) to a peak reached at the end of the stretch. Plotted against stretch velocity, P1a tension increased in direct proportion to stretch velocity (viscous-like) whereas, P2a tension (calculated as peak tension minus P1a tension) increased with stretch velocity to a plateau (visco-elastic). Examined at the peak of a twitch, P1a tension had a slope (viscosity coefficient) of 1.8 kNm−2 per L0 s−1 in fast fibres and 4.7 kNm−2 per L0 s−1 in slow muscle fibres. In the same preparations, P2a tension had a relaxation time of 8 ms in the fast muscle fibres and 25 ms in the slow muscle fibres. The amplitudes of both tension components scaled with the instantaneous twitch tension in qualitatively the same way as the instantaneous fibre stiffness. These fast/slow fibre type differences probably reflect differences in their cross-bridge kinetics.
- Published
- 2001
47. [Untitled]
- Author
-
Gabriel Mutungi and K. W. Ranatunga
- Subjects
Physiology ,Tension (physics) ,Chemistry ,Cell Biology ,Isometric exercise ,Anatomy ,Biochemistry ,Sarcomere ,Twitch contraction ,Tendon ,medicine.anatomical_structure ,Length change ,Time course ,medicine ,Biophysics ,Muscle fibre - Abstract
The sarcomere length change, within a 2 mm region, during end-held isometric contractions in intact rat fast and slow muscle fibre bundles was investigated at 20°C and an initial sarcomere length of 2.68 μm using He–Ne laser diffraction. In some experiments, the fibre segment displacement was monitored with markers (pieces of human hair) placed at regular intervals on the surface of the muscle fibre bundles. The sarcomere length changes, monitored near the proximal end of the bundle (transducer end), during tetanic contractions were similar to those previously reported in frog muscle fibres. Thus, throughout the tension plateau, sarcomere length remained constant (and shortened) but showed evidence of non-uniform sarcomere behaviour (further shortening) during the rapid tension relaxation phase. Such non-uniform behaviour was not seen during twitch contractions. During a twitch contraction, sarcomeres at the proximal end shortened rapidly at first and continued to shorten – or remained shortened – until the tension had relaxed to between 20–23% of its peak value before lengthening back to the original length. The maximum twitch sarcomere shortening (mean ± SEM) was 5.9 ± 0.2% (n = 16) in fast and 5.4 ± 0.3% (n = 14) in slow fibre bundles at 20°C; sarcomere shortening near body temperature (∼35°C) was greater, 8.8 ± 0.2% (n = 7) in fast and 8.1 ± 0.2% (n = 5) in slow fibre bundles. Increasing the initial sarcomere length of a preparation decreased the extent of sarcomere shortening and reducing the amount of sarcomere shortening, by sarcomere length clamping, markedly increased the peak twitch tension without significantly altering the twitch time course. When examined at different positions along muscle fibres, a sarcomere shortening was observed along much of the fibre length in most preparations. However, in about a third of the preparations some sarcomere lengthening was recorded in the distal end, but its amplitude was too small to accommodate the fibre shortening elsewhere. Complementary data were obtained using the surface marker technique. The displacement was largest and in opposite – but fibre shortening – direction in the markers placed ∼0.5–1.0 mm away from the two tendon attachments; the markers placed at or near the centre of the fibre bundle showed the least amount of displacement. The findings suggest that the compliant region, where lengthening occurs, is at fibre ends, i.e. near myotendinous junction.
- Published
- 2000
48. Ion channels of biological membranes: prediction of single channel conductance
- Author
-
Charlotte Adcock, Graham Smith, Kishani M. Ranatunga, Mark S.P. Sansom, and Ian D. Kerr
- Subjects
Chemistry ,Computational chemistry ,Ionization ,Yield (chemistry) ,Conductance ,Biological membrane ,Shaker ,Physical and Theoretical Chemistry ,Electrostatics ,Molecular physics ,Ion channel ,Communication channel - Abstract
The Poisson-Boltzmann equation was solved numerically for models of the pore regions of the Shaker K+ channel and of two glycoporins (LamB and ScrY) to yield electrostatic potential profiles along the pore axes. From these potential profiles, single-channel current-voltage (I–V) relations were calculated. The importance of a proper treatment of the ionisation state of two rings of aspartate sidechains at the mouth of the K+ channel pore emerged from such calculations. The calculated most likely state, in which only two of the eight aspartate sidechains were deprotonated, yielded better agreement with experimental conductance data. An approximate calculation of single-channel conductances based simply on pore geometry yielded very similar conductance values for the two glycoporins. This differed from an␣experimentally determined conductance ratio of ScrY:LamB=10:1. Preliminary electrostatics calculations appeared to reproduce the observed difference in conductance between the two glycoporins, confirming that single-channel conductance is determined by electrostatic as well as geometric considerations.
- Published
- 1999
49. [Untitled]
- Author
-
Kishani M. Ranatunga, Mark S.P. Sansom, and Ian D. Kerr
- Subjects
Pharmacology ,Chemistry ,Sequence analysis ,Stereochemistry ,Organic Chemistry ,Radius ,Domain model ,Voltage-gated potassium channel ,Domain (software engineering) ,Transmembrane domain ,Chemical physics ,Drug Discovery ,Protein secondary structure ,Ion channel - Abstract
Molecular modelling studies of the transmembrane domain, and in particular of the pore-forming region, of voltage-gated K+ channels are reviewed. Sequence analysis methods are used to define transmembrane helices and their orientation within the intact channel protein. A detailed comparison is presented of three models (from different research groups) of the (H5)4 domain. These models have all been generated by systematic attempts to fit experimental data which identify pore-lining sidechains. The models are analysed in terms of pore radius profiles and predicted conductances, as well as the extent of their agreement with published mutagenesis data. An extended pore domain model, (S5-H5-S6)4, which includes the S5 and S6 helices packed around a bulged β-barrel of (H5)4, is also described and analysed.
- Published
- 1999
50. [Untitled]
- Author
-
Farouk Vawda, K. W. Ranatunga, and Michael A. Geeves
- Subjects
Myofilament ,Physiology ,Tension (physics) ,Chemistry ,Drop (liquid) ,Hydrostatic pressure ,Cell Biology ,Anatomy ,Biochemistry ,Sarcomere ,Tibialis anterior muscle ,Phase (matter) ,medicine ,Biophysics ,Tetanic contraction ,medicine.symptom - Abstract
Single intact muscle fibres isolated from the tibialis anterior muscle of the frog were exposed to hydrostatic pressures of 1–10 MPa, at 2–4°C and sarcomere length of 2.1–2.2 μm. The pressure was rapidly released (ca. 1 ms) to atmospheric level (0.1 MPa) during the plateau of a tetanic contraction (Po) and the resultant tension ( =force) transient examined. The pressure release induced tension transient consisted of an initial tension drop coincident with pressure release (ca. 4% Po per MPa, Phase 1), followed by a rapid recovery (Phase 2a) and a slower rise of tension (Phase 2b). Phase 1 was partly due to a length release at fibre ends (ca. 0.1 nm per half-sarcomere per MPa) induced by pressure-release effects on the steel chamber and fibre attachments, and partly due to ‘expansion’ upon pressure release within muscle fibre (ca. 0.2 nm per half-sarcomere per MPa), probably in the myofilaments and cross-bridges. The rate of tension recovery during phase 2a (ca. 600/s) was comparable to that of the quick tension recovery (T1-T2 transition) reported from moderately fast small length releases; the time course of Phase 2b (rate ca. 40/s) was similar to the late phase of tension rise in a tetanus, and hence compared with Phase 4 (T4) of a length release tension transient. Results are compared with the previously reported findings from analogous experiments on Ca2+-activated skinned (rabbit) muscle fibres.
- Published
- 1999
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