Displaying all 9 publications

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  1. Kamilla L, Mansor SM, Ramanathan S, Sasidharan S
    Microsc Microanal, 2009 Aug;15(4):366-72.
    PMID: 19575837 DOI: 10.1017/S1431927609090783
    Clitoria ternatea is known for its antimicrobial activity but the antifungal effects of leaf extract on growth and morphogenesis of Aspergillus niger have not been observed. The extract showed a favorable antifungal activity against A. niger with a minimum inhibition concentration 0.8 mg/mL and minimum fungicidal concentration 1.6 mg/mL, respectively. The leaf extract exhibited considerable antifungal activity against filamentous fungi in a dose-dependent manner with 0.4 mg/mL IC50 value on hyphal growth of A. niger. The main changes observed under scanning electron microscopy after C. ternatea extract treatment were loss of cytoplasm in fungal hyphae and the hyphal wall and its diameter became markedly thinner, distorted, and resulted in cell wall disruption. In addition, conidiophore alterations were also observed when A. niger was treated with C. ternatea leaf extract.
  2. Khan MB, Nisar H, Ng CA, Yeap KH, Lai KC
    Microsc Microanal, 2017 12;23(6):1130-1142.
    PMID: 29212566 DOI: 10.1017/S1431927617012673
    Image processing and analysis is an effective tool for monitoring and fault diagnosis of activated sludge (AS) wastewater treatment plants. The AS image comprise of flocs (microbial aggregates) and filamentous bacteria. In this paper, nine different approaches are proposed for image segmentation of phase-contrast microscopic (PCM) images of AS samples. The proposed strategies are assessed for their effectiveness from the perspective of microscopic artifacts associated with PCM. The first approach uses an algorithm that is based on the idea that different color space representation of images other than red-green-blue may have better contrast. The second uses an edge detection approach. The third strategy, employs a clustering algorithm for the segmentation and the fourth applies local adaptive thresholding. The fifth technique is based on texture-based segmentation and the sixth uses watershed algorithm. The seventh adopts a split-and-merge approach. The eighth employs Kittler's thresholding. Finally, the ninth uses a top-hat and bottom-hat filtering-based technique. The approaches are assessed, and analyzed critically with reference to the artifacts of PCM. Gold approximations of ground truth images are prepared to assess the segmentations. Overall, the edge detection-based approach exhibits the best results in terms of accuracy, and the texture-based algorithm in terms of false negative ratio. The respective scenarios are explained for suitability of edge detection and texture-based algorithms.
  3. Shanmugapriya, Vijayarathna S, Sasidharan S
    Microsc Microanal, 2019 10;25(5):1263-1272.
    PMID: 31383043 DOI: 10.1017/S1431927619014776
    Several microscopy methods have been developed to assess the morphological changes in cells in the investigations of the mode of cell death in response to a stimulus. Our recent finding on the treatment of the IC50 concentration (26.67 μg/mL) of Polyalthia longifolia leaf extract indicated the induction of apoptotic cell death via the regulation of miRNA in HeLa cells. Hence, the current study was conducted to validate the function of these downregulated microRNAs in P. longifolia-treated HeLa cells using microscopic approaches. These include scanning electron microscope (SEM), transmission electron microscope (TEM), and acridine orange/propidium iodide (AO/PI)-based fluorescent microscopy techniques by observing the morphological alterations to cells after transfection with mimic miRNA. Interestingly, the morphological changes observed in this study demonstrated the apoptotic hallmarks, for instance, cell blebbing, cell shrinkage, cytoplasmic and nuclear condensation, vacuolization, cytoplasmic extrusion, and the formation of apoptotic bodies, which proved the role of dysregulated miRNAs in apoptotic HeLa cell death after treatment with the P. longifolia leaf extract. Conclusively, the current study proved the crucial role of downregulated miR-484 and miR-221-5p in the induction of apoptotic cell death in P. longifolia-treated HeLa cells using three approaches-SEM, TEM, and AO/PI-based fluorescent microscope.
  4. Dezfouli MG, Eissazadeh S, Zade SM
    Microsc Microanal, 2014 Aug;20(4):1167-79.
    PMID: 24735566 DOI: 10.1017/S1431927614000701
    This study examines histometrical changes induced by sodium arsenite (SA), as an environmental pollutant, and investigates the protective effect of α-tocopherol on ovaries of SA-treated rats during the prenatal stage until sexual maturity. Rats were classified into groups: control, SA (8 ppm/day), α-tocopherol (100 ppm/day), and SA+α-tocopherol. Treatment was performed from pregnancy until maturation when the rats and ovaries were weighed. The Cavalieri method was used to estimate volume of the ovaries, cortex, medulla, and corpus luteum. The mean diameter of oocytes, granulosa cells, and nuclei were measured and volume was estimated using the Nucleator method. The number of oocytes and thickness of the zona pellucida (ZP) were determined using an optical dissector and orthogonal intercept method, respectively. SA reduced the body and ovary weight, the number of secondary, antral and Graafian oocytes, volume of the ovaries, cortex, medulla and corpus luteum, mean diameter and volume of oocytes in primordial and primary follicles, mean diameter and volume of oocyte nuclei in all types of follicles, and mean thickness of the ZP in secondary and antral follicles. Also, the mean diameter and volume of granulosa cells and their nuclei in antral and Graafian follicles decreased significantly. Vacuolization and vascular congestion in the corpus luteum and an increase in the number of atretic oocytes were seen in the SA group. Most of these parameters were unchanged from the control level in the SA+α-tocopherol group. It was concluded that α-tocopherol supplementation reduced the toxic effects of SA exposure on ovarian tissue in rats.
  5. Aruldass CA, Marimuthu MM, Ramanathan S, Mansor SM, Murugaiyah V
    Microsc Microanal, 2013 Feb;19(1):254-60.
    PMID: 23332129 DOI: 10.1017/S1431927612013785
    Mesua ferrea is traditionally used for treating bleeding piles, fever, and renal diseases. It has been reported to have antimircobial activity. In the present study, antibacterial efficacy of leaf and fruit extracts on the growth and morphology of Staphylococcus aureus is evaluated. Both extracts display good antibacterial activity against S. aureus with a minimum inhibition concentration of 0.048 mg/mL. Both extracts are bacteriostatic at a minimum bacteriostatic concentration of 0.39 mg/mL. The bacteriostatic activity lasts for 24 h, and then cells start to grow as normal as shown in time-kill analysis. Scanning electron microscopy study indicated potential detrimental effect of the extracts of leaf and fruits of M. ferrea on the morphology of S. aureus. The treatment with the extracts caused extensive lysis of the cells, leakage of intracellular constituents, and aggregation of cytoplasmic contents forming an open meshwork of the matrix.
  6. Wong RS, Radhakrishnan AK, Ibrahim TA, Cheong SK
    Microsc Microanal, 2012 Jun;18(3):462-9.
    PMID: 22640960 DOI: 10.1017/S1431927612000177
    Tocotrienols are isomers of the vitamin E family, which have been reported to exert cytotoxic effects in various cancer cells. Although there have been some reports on the effects of tocotrienols in leukemic cells, ultrastructural evidence of tocotrienol-induced apoptotic cell death in leukemic cells is lacking. The present study investigated the effects of three isomers of tocotrienols (alpha, delta, and gamma) on a human T lymphoblastic leukemic cell line (CEM-SS). Cell viability assays showed that all three isomers had cytotoxic effects (p < 0.05) on CEM-SS cells with delta-tocotrienol being the most potent. Transmission electron microscopy showed that the cytotoxic effects by delta- and gamma-tocotrienols were through the induction of an apoptotic pathway as demonstrated by the classical ultrastructural apoptotic changes characterized by peripheral nuclear chromatin condensation and nuclear fragmentation. These findings were confirmed biochemically by the demonstration of phosphatidylserine externalization via flow cytometry analysis. This is the first study showing classical ultrastructural apoptotic changes induced by delta- and gamma-tocotrienols in human T lymphoblastic leukemic cells.
  7. Cilwyn-Shalitha B, Sasidharan S
    Microsc Microanal, 2023 Jun 09;29(3):1153-1167.
    PMID: 37749670 DOI: 10.1093/micmic/ozad023
    The present study investigated the effects of Polyalthia longifolia leaf extract against the growth of HeLa cell xenograft tumor in nude mice and its underlying mechanism. The nude mice xenografted with HeLa cells were treated with 5% DMSO (vehicle control), 20 mg/kg/body weight of etoposide (positive control), and 500 and 1000 mg/kg/body weight of leaf extract, respectively. Antitumor activity was evaluated with apoptosis, proliferation, and angiogenesis using microscopic-based histological and immunohistochemical microanalyses. The tumor tissue histological and immunohistochemical analyses showed that the HeLa tumor cell death was associated with apoptosis and decreased (p < 0.05) expression of Ki-67 in tumor tissues. The extract also inhibits tumor angiogenesis by downregulating (p < 0.05) the expression of VEGF and CD31 in tumor tissues after treatment for 35 days. Conclusively, the P. longifolia leaf extract effectively inhibited HeLa cell xenograft growth in nude mice. The possible mechanism was related to induction of apoptosis, inhibition of tumor HeLa cell proliferation by decreasing the Ki-67 protein expression, and prevention of tumor angiogenesis by reducing VEGF and CD31 protein expression in HeLa cells.
  8. Hemagirri M, Sasidharan S
    Microsc Microanal, 2022 Mar 09.
    PMID: 35260222 DOI: 10.1017/S1431927622000393
    Polyalthia longifolia is known for its anti-oxidative properties, which might contribute to the antiaging action. Hence, the current research was conducted to evaluate the antiaging activity of P. longifolia leaf methanolic extract (PLME) in a yeast model based on morphology using microscopic approaches. Saccharomyces cerevisiae BY611 strain yeast cells were treated with 1.00 mg/mL of PLME. The antiaging activity was assessed by determining the replicative lifespan, total lifespan, vacuole morphology by light microscopy, extra-morphology by scanning (SEM), and intra-morphology by transmission (TEM) electron microscopy. The findings demonstrated that PLME treatment significantly accelerated the replicative and total lifespan of the yeast cells. PLME treatment also delays the formation of large apoptotic-like type 3 yeast cell vacuoles. The untreated yeast cells demonstrated aging morphology via SEM analysis, such as shrinking, regional invaginations, and wrinkled cell surface. The TEM analysis revealed the quintessential aging intracellular morphology such as swollen, wrinkled, or damaged vacuole formation of the circular endoplasmic reticulum, a rupture in the nuclear membrane, fragmentation of the nucleus, and complete damaged cytoplasm. Decisively, the present study revealed the vital role of PLME in the induction of antiaging activity in a yeast model using three microscopic approaches—SEM, TEM, and bright-field light microscope.
  9. Loo CC, Ng SS, Chang WS
    Microsc Microanal, 2022 May 26.
    PMID: 35616223 DOI: 10.1017/S143192762200085X
    The surging interest in manipulating the polarization of piezo/ferroelectric materials by means of light has driven an increasing number of studies toward their light-polarization interaction. One way to investigate such interaction is by performing piezoresponse force microscopy (PFM) while/after the sample is exposed to light illumination. However, caution must be exercised when analyzing and interpreting the data, as demonstrated in this paper, because sizeable photo-response observed in the PFM amplitude image of the sample is shown to be caused by the electrostatic interaction between the photo-induced surface charge and tip. Through photo-assisted Kelvin probe force microscopy (KPFM), positive surface potential is found to be developed near the sample's surface under 405 nm light illumination, whose effects on the measured PFM signal is revealed by the comparative studies on its amplitude curves that are obtained using PFM spectroscopy mode with/without illumination. This work exemplifies the need for complementary use of KPFM, PFM imaging mode, and PFM spectroscopy mode in order to distinguish real behavior from artifacts.
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