9 results on '"Kumaran, Narayanan"'
Search Results
2. A polyol-stevia blended sugar replacer exhibits low glycemic response among human subjects
- Author
-
Allan Wee Ren Ng, Kumaran Narayanan, K.K. Loh, and N. Gupta
- Subjects
Blood Glucose ,0301 basic medicine ,Polymers ,Research Subjects ,Endocrinology, Diabetes and Metabolism ,Organoleptic ,030209 endocrinology & metabolism ,Erythritol ,Xylitol ,Beverages ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Glucosides ,Polyol ,Humans ,Stevia ,Ingestion ,Medicine ,Single-Blind Method ,Food science ,Sugar ,Glycemic ,Ethics ,chemistry.chemical_classification ,030109 nutrition & dietetics ,Nutrition and Dietetics ,Plant Extracts ,business.industry ,Malaysia ,Glucose ,Glycemic index ,chemistry ,Food ,Glycemic Index ,Sweetening Agents ,Diterpenes, Kaurane ,Sugars ,business - Abstract
Consumption of sugars in food and beverages has increased at an alarming rate. While excessive daily sugar intake has been well-associated as the onset of medical complications, additional sugars are still used in manufactured food products just to satisfy the consumers' needs. Hence, there is a need to develop sugar replacers that have low glycemic response without compromising the organoleptic characteristics of food products. This study aimed to determine if SUITENA™, a novel sweetener containing erythritol, xylitol, and Stevia, has low glycemic response upon consumption by human subjects.Six human subjects were randomly chosen and were healthy at the point of experimentation. Capillary blood was collected via finger-prick method to monitor the glycemic response of every individual for 90 min after ingestion of sugar solution.It was found that the mean area under the curve (AUC) of the dextrose standard was 11.8-fold higher (p 0.05) than the AUC of SUITENA™. SUITENA™ was not able to increase blood glucose level for up to 90 min while a spike in blood glucose level was observed from 15 min post-consumption of dextrose solution. We found that SUITENA™ has elicited a glycemic response 8% relative to the standard. Such low glycemic response has been reported by studies on other novel sugars.This preliminary finding suggested that SUITENA™ is a healthier alternative to fast sugars due to its low glycemic response. A larger sampling size is required to confirm the results.
- Published
- 2019
3. RFP-based method for real-time tracking of invasive bacteria in a heterogeneous population of cells
- Author
-
Edmund Ui Hang Sim, Choon Weng Lee, Malik Adewoyin, Kumaran Narayanan, and Rasaq Olajide Akinsola
- Subjects
Imaging flow cytometry ,media_common.quotation_subject ,Biophysics ,Biology ,Biochemistry ,Green fluorescent protein ,Flow cytometry ,Escherichia coli ,medicine ,Humans ,Internalization ,Molecular Biology ,media_common ,Bacteria ,Staining and Labeling ,medicine.diagnostic_test ,Reproducibility of Results ,Cell Biology ,Flow Cytometry ,biology.organism_classification ,Cell biology ,Luminescent Proteins ,Heterogeneous population ,Cytosol ,Eukaryotic Cells ,HEK293 Cells ,A549 Cells ,MCF-7 Cells ,Function (biology) - Abstract
Quantification of bacterial invasion into eukaryotic cells is a prerequisite to unfold the molecular mechanisms of this vector's function to obtain insights for improving its efficiency. Invasion is traditionally quantified by antibiotic protection assays that require dilution plating and counting of colony-forming units rescued from infected cells. However, to differentiate between attached and internalized bacteria vector, this assay requires supplementation by a time-consuming and tedious immunofluorescence staining, making it laborious and reduces its reliability and reproducibility. Here we describe a new red fluorescent protein (RFP)-based high-throughput and inexpensive method for tracking bacterial adherence and internalization through flow cytometry to provide a convenient and real-time quantification of bacterial invasiveness in a heterogeneous population of cells. We invaded MCF-7, A549, and HEK-293 cells with the E. coli vector and measured RFP using imaging flow cytometry. We found high cellular infection of up to 70.47% in MCF-7 compared to 27.4% and 26.2% in A549 and HEK-293 cells, respectively. The quantitative evaluation of internalized E. coli is rapid and cell-dependent, and it distinctively differentiates between attached and cytosolic bacteria while showing the degree of cellular invasiveness. This imaging flow cytometry approach can be applied broadly to study host-bacteria interaction.
- Published
- 2021
4. Large BACs transfect more efficiently in circular topology
- Author
-
Kumaran Narayanan, Farooq O. Al-Ajli, Andrew N. Osahor, and Yin Cheng Wong
- Subjects
Chromosomes, Artificial, Bacterial ,Genetic Vectors ,Optical Imaging ,Biophysics ,Intron ,DNA ,Cell Biology ,Transfection ,Gene delivery ,Biology ,Topology ,Biochemistry ,genomic DNA ,chemistry.chemical_compound ,Exon ,Plasmid ,chemistry ,Regulatory sequence ,Cell Line, Tumor ,Humans ,Molecular Biology ,Plasmids - Abstract
The effect of DNA topology on transfection efficiency of mammalian cells has been widely tested on plasmids smaller than 10 kb, but little is known for larger DNA vectors carrying intact genomic DNA containing introns, exons, and regulatory regions. Here, we demonstrate that circular BACs transfect more efficiently than covalently closed linear BACs. We found up to 3.1- and 8.9- fold higher eGFP expression from circular 11 kb and 100 kb BACs, respectively, compared to linear BACs. These findings provide insights for improved vector development for gene delivery and expression studies of large intact transgenes in mammalian cells.
- Published
- 2021
5. An antibody binding-based fluorescent assay for the rapid quantification of globotriaosylceramide levels in human Fabry cells
- Author
-
Kumaran Narayanan and Allan Wee Ren Ng
- Subjects
Biophysics ,Globotriaosylceramide ,Fluorescent Antibody Technique ,Urine ,Immunofluorescence staining ,01 natural sciences ,Biochemistry ,03 medical and health sciences ,chemistry.chemical_compound ,medicine ,Humans ,Molecular Biology ,030304 developmental biology ,0303 health sciences ,biology ,Trihexosylceramides ,010401 analytical chemistry ,Cell Biology ,medicine.disease ,Antigen binding ,Fluorescence ,Fabry disease ,Molecular biology ,0104 chemical sciences ,chemistry ,Cell culture ,biology.protein ,Fabry Disease ,Antibody - Abstract
Fabry disease is caused by reduced α-GAL A activity and accumulation of globotriaosylceramide (Gb3). Here, we describe a microplate Gb3 assay using fluorophore-tagged antibody and crude cellular lipid extracts. The assay is able to detect higher Gb3 concentrations in human Fabry cells compared to non-diseased cells. This result was verified by immunofluorescence staining that revealed large amounts of Gb3 deposits in Fabry cell lines, demonstrating the accuracy of this method. This assay may provide the basis for detecting Fabry disease by quantifying Gb3 deposits from human biological samples, for example, from urine and blood.
- Published
- 2021
6. Phage N15 protelomerase resolves its tos recognition site into hairpin telomeres within mammalian cells
- Author
-
Pei Sheng Liew, Nikolai V. Ravin, Choon Weng Lee, Yee Choy Chew, Edmund Ui Hang Sim, Kumaran Narayanan, Qingwen Chen, and Allan Wee Ren Ng
- Subjects
DNA Replication ,Biophysics ,beta-Globins ,medicine.disease_cause ,01 natural sciences ,Biochemistry ,Genome ,Mice ,Viral Proteins ,03 medical and health sciences ,chemistry.chemical_compound ,Plasmid ,Escherichia coli ,medicine ,Animals ,Humans ,Gene silencing ,Telomerase ,Molecular Biology ,Gene ,030304 developmental biology ,RecBCD ,Enzyme Precursors ,0303 health sciences ,010401 analytical chemistry ,DNA ,Cell Biology ,0104 chemical sciences ,Telomere ,Cell biology ,chemistry ,NIH 3T3 Cells ,Genetic Engineering ,HeLa Cells - Abstract
Phage N15 protelomerase (TelN) cleaves double-stranded circular DNA containing a telomerase-occupancy-site (tos) and rejoins the resulting linear-ends to form closed-hairpin-telomeres in Escherichia coli (E. coli). Continued TelN expression is essential to support resolution of the linear structure. In mammalian cells, no enzyme with TelN-like activities has been found. In this work, we show that phage TelN, expressed transiently and stably in human and mouse cells, recapitulates its native activities in these exogenous environments. We found TelN to accurately resolve tos-DNA in vitro and in vivo within human and mouse cells into linear DNA-containing terminal telomeres that are resistant to RecBCD degradation, a hallmark of protelomerase processing. In stable cells, TelN activity was detectable for at least 60 days, which suggests the possibility of limited silencing of its expression. Correspondingly, linear plasmid containing a 100 kb human β-globin gene expressed for at least 120 h in non-β-globin-expressing mouse cells with TelN presence. Our results demonstrate TelN is able to cut and heal DNA as hairpin-telomeres within mammalian cells, providing a tool for creating novel structures by DNA resolution in these hosts. The TelN protelomerase may be useful for exploring novel technologies for genome interrogation and chromosome engineering.
- Published
- 2019
7. Investigating the decay rates of Escherichia coli relative to Vibrio parahemolyticus and Salmonella Typhi in tropical coastal waters
- Author
-
Choon Weng Lee, Chui Wei Bong, Edmund Ui Hang Sim, Kumaran Narayanan, Ching Ching Ng, and Angie Yee Fang Ng
- Subjects
Salmonella ,Environmental Engineering ,Colony Count, Microbial ,Chemical Fractionation ,medicine.disease_cause ,Salmonella typhi ,Microbiology ,Escherichia coli ,medicine ,Seawater ,Particle Size ,Waste Management and Disposal ,Water Science and Technology ,Civil and Structural Engineering ,Tropical Climate ,biology ,Ecological Modeling ,Vibrio parahaemolyticus ,Malaysia ,biology.organism_classification ,Pollution ,Enterobacteriaceae ,Vibrio ,Bacteria ,Environmental Monitoring - Abstract
Using the size fractionation method, we measured the decay rates of Escherichia coli, Salmonella Typhi and Vibrio parahaemolyticus in the coastal waters of Peninsular Malaysia. The size fractions were total or unfiltered,250 μm,20 μm,2 μm,0.7 μm,0.2 μm and0.02 μm. We also carried out abiotic (inorganic nutrients) and biotic (bacterial abundance, production and protistan bacterivory) measurements at Port Dickson, Klang and Kuantan. Klang had highest nutrient concentrations whereas both bacterial production and protistan bacterivory rates were highest at Kuantan. We observed signs of protist-bacteria coupling via the following correlations: Protistan bacterivory-Bacterial Production: r = 0.773, df = 11, p0.01; Protist-Bacteria: r = 0.586, df = 12, p0.05. However none of the bacterial decay rates were correlated with the biotic variables measured. E. coli and Salmonella decay rates were generally higher in the larger fraction (0.7 μm) than in the smaller fraction (0.7 μm) suggesting the more important role played by protists. E. coli and Salmonella also decreased in the0.02 μm fraction and suggested that these non-halophilic bacteria did not survive well in seawater. In contrast, Vibrio grew well in seawater. There was usually an increase in Vibrio after one day incubation. Our results confirmed that decay or loss rates of E. coli did not match that of Vibrio, and also did not correlate with Salmonella decay rates. However E. coli showed persistence where its decay rates were generally lower than Salmonella.
- Published
- 2011
8. Crude protein extraction protocol for phage N15 protelomerase in vitro enzymatic assays
- Author
-
Kumaran Narayanan and Qingwen Chen
- Subjects
chemistry.chemical_classification ,Telomerase ,Bacteria ,Functional analysis ,Biophysics ,Cell Biology ,Telomere ,Biology ,Biochemistry ,Genome ,In vitro ,Enzymatic Assays ,Enzyme ,chemistry ,Protein purification ,Escherichia coli ,Bacteriophages ,Molecular Biology - Abstract
The phage N15 protelomerase enzyme (TelN) is essential for the replication of its genome by resolution of its telRL domain, located within a telomerase occupancy site (tos), into hairpin telomeres. Isolation of TelN for in vitro processing of tos, however, is a highly complex process, requiring multiple purification steps. In this study a simplified protocol for crude total protein extraction is described that retains the tos-cleaving activity of TelN for at least 4 weeks, greatly simplifying in vitro testing of its activity. This protocol may be extended for functional analysis of other phage and bacterial proteins, particularly DNA-processing enzymes.
- Published
- 2011
9. Intact recombineering of highly repetitive DNA requires reduced induction of recombination enzymes and improved host viability
- Author
-
Kumaran Narayanan
- Subjects
Chromosomes, Artificial, Bacterial ,Cell Survival ,Biophysics ,Biology ,medicine.disease_cause ,Biochemistry ,Recombineering ,law.invention ,chemistry.chemical_compound ,law ,medicine ,Repeated sequence ,Molecular Biology ,Escherichia coli ,Repetitive Sequences, Nucleic Acid ,Recombination, Genetic ,Genetics ,Bacterial artificial chromosome ,DNA ,Cell Biology ,Recombinant Proteins ,Cell biology ,Restriction site ,chemistry ,Enzyme Induction ,Recombinant DNA ,Trinucleotide repeat expansion - Abstract
Recombineering technology permits flexible engineering of large DNA in Escherichia coli without dependence on suitably placed restriction sites. However, recombineering is limited for modifying highly repetitive DNA because of its potential to trigger instability by uncontrolled self-recombination of the repeats. In this study, induction of the recombineering enzymes and growth condition of the host are optimized to demonstrate intact modification of bacterial artificial chromosomes (BACs) containing long arrays of centromeric alpha satellite repeats. This optimized recombineering protocol may be useful for manipulation of other biologically important repetitive DNAs, including trinucleotide repeat expansions and homologous gene families, to facilitate their functional studies.
- Published
- 2008
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.