Samlee Mankhetkorn - Academia.edu (original) (raw)

Papers by Samlee Mankhetkorn

Biochemistry and Cell Biology, 2002

Anne-Cathrine Scheen, Reidar Elven, and Christian Brochmann A molecular-morphological approach so... more Anne-Cathrine Scheen, Reidar Elven, and Christian Brochmann A molecular-morphological approach solves taxonomic controversy in arctic Draba (Brassicaceae) Suneetha Alokam, C.C. Chinnappa, and David M. Reid Red/far-red light mediated stem elongation and anthocyanin accumulation in Stellaria longipes: differential response of alpine and prairie ecotypes Suzuki Mahoro Individual flowering schedule, fruit set, and flower and seed predation in Vaccinium hirtum Thunb. (Ericaceae) L.R. Little Investigating competitive interactions from spatial patterns of trees in multispecies boreal forests: the random mortality hypothesis revisited Instructions to Authors I-1 Recommandations aux auteurs R-1 February / février Editorial / Éditorial iii COMMENTARY / COMMENTAIRE D.H.S. Richardson Reflections on lichenology: achievements over the last 40 years and challenges for the future 101 ARTICLES R.D. Geil and F.C. Guinel Effects of elevated substrate-ethylene on colonization of leek (Allium porrum) by the arbuscular mycorrhizal fungus Glomus aggregatum 114 Rhoda L. Burrows and Francis L. Pfleger Arbuscular mycorrhizal fungi respond to increasing plant diversity 120

A simple and easy to implement numerical method is proposed in order to considerably simplify the... more A simple and easy to implement numerical method is proposed in order to considerably simplify the experimental calibration procedure of C-SNARF-1 indicator used for ratiometric pH sensing. Usually, calibration is based on the measurement of fluorescence spectra using perfectly calibrated equipment at extreme pH values. The calibration solutions must be extremely well controlled in terms of indicator concentration and path length. Also, the optical equipment used must be well controlled and excitation energy as well as fluorescence collection efficiency must be perfectly constant over the whole calibration procedure. The method we propose is based on the fact that the emission fluorescence energy does not only depend on pH but also on the excitation wavelength. In this paper, we propose a model describing the evolution of the emitted energy as a function of pH and excitation wavelength. We show that the emitted energy evolves linearly with pH and we express this linear evolution as a...

Proceedings of the 11th International Joint Conference on Biomedical Engineering Systems and Technologies, 2018

Organic functions of the human body are related to biological constants. Variations of these cons... more Organic functions of the human body are related to biological constants. Variations of these constants, among them pH, induce pathological troubles. The general goal of our work is to fabricate a fluorescent pH sensor at the end of an optical fiber for in vivo pH measurements. One difficulty using fluorescence indicators is the need to perform an accurate calibration. In this communication, we present methods used to simplify and potentially avoid calibration procedures of fluorescence indicators. The first method concerns the simplification of calibration procedures making them independent of the indicator's concentration, path length and equipment used. The second method concerns modelling the fluorescence emission of the molecules as a function of pH only. This model is used to fit the exact shape of C-SNARF-1 fluorescence spectra obtained at any pH. Subsequently, the pH of a solution can be computed with an accuracy of 0.1 pH unit without the calibration procedure employed up to now. These methods constitute the first steps toward calibration free pH measurements. They can be applied to any fluorescent indicator exhibiting a dual emission peak. As a conclusion, this is the first time that fluorescence properties of C-SNARF-1 are fully mathematically described.

Materials Today: Proceedings, 2019

The goal of this work concerns a new method to substantially increase the sensitivity of a fluore... more The goal of this work concerns a new method to substantially increase the sensitivity of a fluorescence pH sensor. The method is based on a double silanization method. Two methods are compared: one using APTMS (3-Aminopropyl)trimethoxysilane) only and another one using both APTMS and APDMS (3-Aminopropyl)dimethoxymethylsilane). Using the second method, sensor's sensitivity is improved by more than 500 %.

Sensors and Actuators B: Chemical, 2017

We investigated the possibility to grow molecularly porous amino-silane layers on glass-like subs... more We investigated the possibility to grow molecularly porous amino-silane layers on glass-like substrates. The goal of this work is to show that it is possible to substantially increase the sensitivity of a fluorescence sensor by adjusting the functionalization strategy. Two methods are studied, one using APTMS only and another one using both APTMS and APDMS. We show that, using the second method, sensor sensitivity is improved by a factor of about 5. In order to demonstrate this, we applied the technique to the grafting of fluorescein in order to build a fluorescence pH sensor.

International journal of molecular imaging, 2016

Physiological responses such as chronic inflammation and angiogenesis could be used as biomarkers... more Physiological responses such as chronic inflammation and angiogenesis could be used as biomarkers for early detection of cancer with noninvasive imaging modalities. The present study reports the application of magnetic resonance imaging instrument to image the binding of ferrioxamine with hemin that allows visualizing the chronic inflammation foci of lung tissue of immunocompromised rats xenografted using small cell lung carcinoma. A low concentration of ferrioxamine (0.05 ± 0.02 μM·kg(-1) of rat weight) deposited on tissue outside the vasculature was found to diffuse across the capillary walls to the interstitial space and inflammation foci, which provided a clear enhancement of T1-weighted gradient-echo sequence images. Ferrioxamine imaging allowed the determination of inflammatory sites and their localization in 3D fat-suppressed maximum intensity projections. The smallest dimension of foci that can be clearly determined is about 0.1 mm(3). In concomitant to the in vivo imaging, ...

Archives of Dermatological Research, 2016

Keloids are pathologic scars defined as dermal fibrotic tumors resulting from a disturbance of sk... more Keloids are pathologic scars defined as dermal fibrotic tumors resulting from a disturbance of skin wound healing process. Treatments against keloids are multiple, sometimes empirical and none of them really provides an effective tool for physicians. The lack of effective treatments is correlated with the poor understanding of keloid pathogenesis. To fill this gap, researchers need strong models mimicking keloids as closely as possible. The objective of this study was to establish in vitro a new reconstructed keloid model (RKM), by combining fibroblasts extracted from the three major area of a keloid (center, periphery, non-lesional) in a three-dimensional biomaterial. To this aim, fibroblasts of three keloid locations were extracted and characterized, and then integrated in a hydrated collagen gel matrix during a three-step procedure. The heterogeneity of fibroblasts was assessed according to their proliferative and remodeling capacities. RKMs were further visualized and characterized by both light and scanning electron microscopy. This reconstructed keloid model should be very useful for investigating keloid fibroblasts function in conditions mimicking in vivo situation. Moreover, RKM should also be a suitable model for either drug study and discovery or innovative approaches using medical devices both during cancer and cancer-like disease investigation.

Srinagarind Medical Journal ศรีนครินทร์เวชสาร, Apr 5, 2013

Background and Objective: Maprang or Marian plum (Bouae burmanica) seeds are the leftover from lo... more Background and Objective: Maprang or Marian plum (Bouae burmanica) seeds are the leftover from local fruit consumption. Since seeds have purple color, it may contain the pigments which are polyphenols. This study aimed to investigate basic physicochemical properties and evaluate anti-proliferative activity of Maprang seed extracts against drug-sensitive and resistant leukemic and lung cancer cells. Methods: Maprang seeds were extracted in serial manner with chloroform, acetonitrile, ethanol and water, respectively. The absorption spectra were analyzed and anti-proliferative activities of the extracts were evaluated against doxorubicin-sensitive and-resistant leukemic and lung cancer cells (K562, K562/adr, GLC4 and GLC4/adr). Furthermore, the morphological changes of cancer cells treated with the extracts were investigated.

Proanthocyanidin and other phenolic compounds may potentially reduce the risk of cardiovascular d... more Proanthocyanidin and other phenolic compounds may potentially reduce the risk of cardiovascular diseases and cancer, as well as having antioxidant, anti-inflammatory and chemoprotective properties. Proanthocyanidin (PA) and cyanidin 3-glucoside (C3G), a polyphenolic compound of purple color found in purple glutinous rice (Oryza sativa L.), may also manifest these positive effects. This research evaluated the effect of PA and C3G on X63, a mouse-plasma cancer cell line of myeloma cells. PA and C3G were extracted from the purple rice bran of a local, Thailand, purple, rice genotype (Kum Doi Saket). The results showed that the amount of C3G extract from the rice genotype was 54.47 mg/ 100 g rice bran. The cytotoxicity of the crude PA extract was demonstrated by a dose-dependent decrease in the percentage cell viability of the control in the PA group. A significant difference (p<0.05) began at 100 ∝g/ml and IC50 occurred at 62.29 ∝g/ml. The C3G extract also exhibited a dose-dependent decrease, but the significant difference (p<0.05) began at 10 ∝M and IC50 occurred at 8.4 ∝M. This research demonstrated a dose-related cytotoxic effect on cancer cells by the crude PA and C3G extracts from purple glutinous rice. The results indicated the benefit of the purple rice genotypes as a functional food with potential anticancer properties.

The Open Drug Delivery Journal, 2008

The objectives of this study were to investigate the behavior of flavonoids in an aqueous physiol... more The objectives of this study were to investigate the behavior of flavonoids in an aqueous physiological buffer and to determine the structural and functional group substitution which is responsible for their anticancer action. The deprotonated anionic form of 7 flavonoids can easily be determined using spectrophotometry, and owing to its charged state, is highly soluble in aqueous physiological buffer and is not prone to aggregation. The protonated form of these 7 flavonoids is much less soluble and tends to aggregate following precipitation. For all flavonoids studied except catechin and 5,5-dihydroxy-6,7,3 ,4-tetramethoxyflavone, it was possible to determine the rates of deprotonation; pKa value of eriodictyol, apigenin, kaempferol, quercetin, WP 279, and WP 283 was equal to 7.00, 8.72, 7.86, 8.30, 7.70 and 9.90, respectively. The methoxyl group substitutions in place of hydrogen atoms and/or hydroxyl groups at various positions of carbon atoms in ring A, B and C particularly WP 283 resulted in an increase in the solubility, lipophilicity, and specifically its anticancer efficacy (by 60-fold). The neutral forms of flavonoids are predominantly active molecules and the active sites responsible for anticancer activity are found in ring A and C, especially C4=O, C5-OH and C2=C3.

Materials Letters, 2015

This research was designed to visualize cellular responsein particular the generation of intracel... more This research was designed to visualize cellular responsein particular the generation of intracellular ROSto stimulation by polycyclic aromatic hydrocarbon (PAH). We used chloroauric acid (HAuCl 4) as a molecular probe for visualizing intracellular ROS generated by the stimulation of benzo[a]pyrene (BaP). The chloroauric acid undergoes a spontaneous reduction reaction, assisted by the intracellular ROS, into gold nanoclusters (AuNCs). As a result, we can visualize the ROS via optical imaging technique. According to MTT assay, the chloroauric acid exhibited good biocompatibility. The AuNCs produced in the cells were approximately 2-3 nm in diameter with a green fluorescent property. Cellular imaging showed that BaP induced the formation of AuNCs within the cells, leading to a high relative cellular fluorescent intensity with a considerable extent of scatter light. Thus, this probe is an efficient molecular imaging probe for visualizing intracellular ROS.

Pharmaceutical Biology, 2012

Context: The number of patients with cancer is increasing. New therapeutic agents to overcome dru... more Context: The number of patients with cancer is increasing. New therapeutic agents to overcome drug-resistant tumors are urgently needed. Cyrtosperma johnstonii N.E. Br. (Araceae) is used for treatment of cancer in Thai traditional medicine. This study aimed to evaluate antioxidant activity and cytotoxicity of C. johnstonii extracts on human cancer cells. Materials and methods: Dried powder of C. johnstonii rhizomes was extracted with several solvents. The 0.1 mg/ ml extract solution was tested for antioxidant activity by 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and ferric reducing antioxidant power (FRAP) assays. Color formation from 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide was used to determine cell viability. Standardization of the extract was performed by high-performance liquid chromatography (HPLC) with photodiode array detector at 254 and 360 nm. Cell cycle arrest was evaluated by flow cytometry after 5 min, 12 h and 24 h treated with 20 µg/ml of the acetone extract. Results: The acetone extract exhibited the highest phenolic content and antioxidant activity (TEAC and EC values = 19.2 ± 0.14 and 19.2 ± 0.31 mM/mg, respectively). The IC 50 values for leukemia ranged from 11 ± 1 to 29 ± 3 µg/ml and from 5 ± 2 to 6 ± 0 µg/ml for small cell lung carcinoma cells. Cell cycle arrest occurred at the G2/M phase followed by apoptosis. HPLC analysis revealed that rutin is the major constituents of the extract. Discussion and conclusion: The acetone extract of C. johnstoni is a promising source of natural antioxidants and anticancer. The extract inhibits cancer cells effectively with less effect on normal cells.

Molecular Cancer, 2010

Background Multidrug resistance (MDR) is a major obstacle in cancer treatment and is often the re... more Background Multidrug resistance (MDR) is a major obstacle in cancer treatment and is often the result of overexpression of the drug efflux protein, P-glycoprotein (P-gp), as a consequence of hyperactivation of NFκB, AP1 and Nrf2 transcription factors. In addition to effluxing chemotherapeutic drugs, P-gp also plays a specific role in blocking caspase-dependent apoptotic pathways. One feature that cytotoxic treatments of cancer have in common is activation of the transcription factor NFκB, which regulates inflammation, cell survival and P-gp expression and suppresses the apoptotic potential of chemotherapeutic agents. As such, NFκB inhibitors may promote apoptosis in cancer cells and could be used to overcome resistance to chemotherapeutic agents. Results Although the natural withanolide withaferin A and polyphenol quercetin, show comparable inhibition of NFκB target genes (involved in inflammation, angiogenesis, cell cycle, metastasis, anti-apoptosis and multidrug resistance) in dox...

Metal-Based Drugs, 1995

The new potential tracer of bone imaging, AHBDP-Sn(II)-TcO.3H20 was synthesized by reducing the T... more The new potential tracer of bone imaging, AHBDP-Sn(II)-TcO.3H20 was synthesized by reducing the TcO4" to TcO 2+ in the presence of AHBDP and Sn(ll)'s reducing agent. We found that tin rapidly forms a stable complex with AHBDP, giving AHBDP-Sn(II).3H20. In the excess of AHBDP-Sn(ll).3H20, the AHBDP-Sn(II).3H20 coordinates with TcO 2+ to give AHBDP-Sn(II)-TcO.3H20 which could polymerise or oligomerise to give hydrophobic species. The overall process appears as a first-order reaction (k= 0.67 +_. 0.005 s'l). In rats, the fixation of AHBDP-Sn(II)-99mTcO. 3H20 on bone is homogeneous and the scintigraphic images have the same quality as those of 1-hydroxymethane-l,l-diphosphonate-Technetium (HMDp-99mTc). The activity in non-target organs was neglible.

Free Radical Biology and Medicine, 1994

The oxidation of sodium diethyldithiocarbamate (DDC) by hydrogen peroxide or superoxide radicals ... more The oxidation of sodium diethyldithiocarbamate (DDC) by hydrogen peroxide or superoxide radicals has been investigated. Hydrogen peroxide oxidizes DDC, leading to the formation of a hydrated form of disulfiram, a dimer of DDC having a disulfide group. In equimolar conditions, the overall process appears as a first-order reaction (k = 0.025 +/- 0.005 s-1), the first step being a second-order reaction (k = 5.0 +/- 0.1 mol-1.1.s-1). No radical intermediate was observed in this process. In the presence of an excess of any of the reagents, the hydrated form of disulfiram transforms into different products corresponding to the fixation of oxygen by sulfur atoms or replacement of C = S group by ketone function, in the presence of an excess of hydrogen peroxide. Superoxide anions (produced by steady-state 60Co gamma-radiolysis) oxidize DDC, yielding similar products to those obtained with hydrogen peroxide with a maximum oxidation G-value of 0.3 mumol.J-1. The rate constant k(O2.- + DDC) is equal to 900 mol-1.1.s-1.

European Journal of Pharmaceutics and Biopharmaceutics, 2011

In this study, quercetin (QCT), a flavonoid with high anticancer potential, was loaded into polym... more In this study, quercetin (QCT), a flavonoid with high anticancer potential, was loaded into polymeric micelles of PEG-OCL (poly(ethylene glycol)-b-oligo(e-caprolactone)) with naphthyl or benzyl end groups in order to increase its aqueous solubility. The cytostatic activity of the QCT-loaded micelles toward different human cancer cell lines and normal cells was investigated. The results showed that the solubility of QCT entrapped in mPEG750-b-OCL micelles was substantially increased up to 1 mg/ml, which is approximately 110 times higher than that of its solubility in water (9 lg/ml). The average particle size of QCT-loaded micelles ranged from 14 to 19 nm. The QCT loading capacity of the polymeric micelles with naphthyl groups was higher than that with benzyl groups (10% and 6%, respectively). QCT-loaded, benzyland naphthyl-modified micelles effectively inhibited the growth of both sensitive and resistance cancer cells (human erythromyelogenous leukemia cells (K562) and small lung carcinoma cells (GLC4)). However, the benzyl-modified micelles have a good cytocompatibility (in the concentration range investigated (up to 100 lg/ml), they are well tolerated by living cells), whereas their naphthyl counterparts showed some cytotoxicity at higher concentrations (60-100 lg/ml). Flow cytometry demonstrated that the mechanism underlying the growth inhibitory effect of QCT in its free form was inducing cell cycle arrest at the G2/M phase. Benzyl-modified micelles loaded with QCT also exhibited this cycle arresting the effect of cancer cells. In conclusion, this paper shows the enhancement of solubility and cell cycle arrest of QCT loaded into micelles composed of mPEG750-b-OCL modified with benzyl end groups. These micelles are therefore considered to be an attractive vehicle for the (targeted) delivery of QCT to tumors.

Chemico-Biological Interactions, 1999

P-glycoprotein (P-gp) is a membranous ATPase responsible for the multidrug resistance phenotype. ... more P-glycoprotein (P-gp) is a membranous ATPase responsible for the multidrug resistance phenotype. The effect on P-gp-mediated transport of anthracyclines of cell irradiation in the presence of 2,2-diphenyl-5-[N-1-(o-azidophenyl)ethylamino]valeronitrile (VP*), a photoactivable analogue of verapamil was studied in viable K562/ADR cells. The derivatives were daunorubicin (DNR), idarubicin (IDA), 8-(S)-fluoro-idarubicin (F-IDA), 2%-bromo-4%-epidaunorubicin (Br-DNR) and pirarubicin (PIRA). It was observed that the irradiation in the presence of the verapamil analogue was unable to completely inhibit the P-gp-mediated efflux of anthracyclines and we estimated that P-gp retained 10-20% of its ability to pump these toxins. The ability of verapamil, DNR, IDA, F-IDA, Br-DNR and PIRA to inhibit the effect of VP* was studied. For this purpose, cells were irradiated in the presence of VP* and various concentrations of either verapamil or of one of the anthracyclines and then the P-gp

Chemico-Biological Interactions, 2001

Resistance to chemotherapeutic agent is a major cause of treatment failure in patients with cance... more Resistance to chemotherapeutic agent is a major cause of treatment failure in patients with cancer. In many cases, the primaly mechanism leading to a multidrug-resistant phenotype is the plasma-membrane localized overexpression of drug efflux transporters, such as P-glycoprotein. However, acidic intracellular organelles seem also to participate in resistance to chemotherapeutic drugs and the determination of the pH of these organelles is of importance. In the present study we have used a new fluorescent derivative of verapamil, 2-2-diphenyl-5-[(methylaminomethyl)anthracene] pentanenitrile (EDP 96), and show that it is an efficient inhibitor of the P-gp-mediated efflux of anthracycline in K562 resistant cells. The fluorescence of EDP 96 is environmental and pH sensitive. EDP 96 is a weak base (pKa=6.0) and its accumulation into K562 cells is accompanied by a significant fluorescence increase due to its entry of the drug into acidic regions in the cells. We have used this properties to develop a new method to accurately determine the pH of acidic organelle.

Chemical and Pharmaceutical Bulletin, 2005

We sought to investigate the early biological effects of chlorpyrifos among 53 Thai fruit farm wo... more We sought to investigate the early biological effects of chlorpyrifos among 53 Thai fruit farm workers by measuring the plasma cholinesterase (PChE) and red blood cell cholinesterase (AChE) activities, a biomarker of organophosphate (OPs) pesticide during one fruit crop. The ChE activity (V m /K m) was spectrophotometrically analyzed before and after exposing to chlorpyrifos. The V m /K m values of both non-spraying and spraying seasons are found as normal distribution pattern. The median PChE and AChE activities among farm workers in the non-spraying season were 2.3؋10 ؊3 s ؊1 and 7.26؋10 ؊5 s ؊1 , respectively. The median PChE and AChE activities of the farm workers in the spraying season were 2.02؋10 ؊3 s ؊1 and 5.95؋10 ؊5 s ؊1 , respectively. The mean V m /K m values of PChE shifted left (t-test, p‫,)310.0؍‬ indicating a decrease in PChE activity in the farm workers exposed to chlorpyrifos. However, the V m /K m values of AChE in nonspraying season and in the spraying season were not different (t-test, p‫.)642.0؍‬ We propose that PChE activity can be used as a biomarker for monitoring early toxicity induced by chlorpyrifos insecticide.