Browsing by Author "Gunasekera, S."

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Focal seizures as first presentation of Pepper syndrome in a six-week-old girl
(Sri Lanka College of Paediatricians, 2022) Sandakelum, U.; Balasubramaniam, R.; Fernando, M.; Gunasekera, S.; Ganewatte, E.; Fernando, S.; Dissanayake, D.
No abstract available
Frequent falls and gaze palsy in two patients
(Ceylon College of Physicians, 2000) Seneviratne, S; Ranawaka, U.; Gunasekera, S.; Senanayake, B.; Fernando, A.; Dissanayake, S.; Wijesekera, J.
Isolation of cysteine-rich peptides from the deep-sea marine sponge Stryphnus fortis and determination of its antimicrobial effect
(Institute of Chemistry Ceylon Adamantane House, Rajagiriya, Sri Lanka., 2020) Kosgahakumbura, K. N. M. L. N; Hettiarachchi, C. M; Jayasinghe, R. P. P. K.; Cárdenas, P.; Gunasekera, S.
Cysteine-rich peptides are a promising resource for a wide range of pharmacological applications such as development of drug leads and as scaffolds for potential oral drug delivery due to their stable disulfide framework. A handful of these compounds have been isolated from marine sponges and it is speculated that plenty of them remain unexplored. In the present study, four peptides A, B, C and D containing three disulfides were isolated from the aqueous extract of the deep-sea marine sponge Stryphnus fortis (Demospongiae, Tetractinellida, Ancorinidae) from Norway, and were further purified using RP-HPLC (Reverse Phase High Performance Liquid Chromatography). The mass spectroscopic analysis using MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization- Time Of Flight) revealed monoisotopic masses of 3331.809 Da [M+H]+, 3349.731 Da [M+H]+, 3517.973 Da [M+H]+, 3917.61 Da [M+H]+respectively for the four peptides A, B, C and D. The antimicrobial activity was screened using a peptide adapted Micro dilution assay against E. coli (ATCC 25922), S. aureus (ATCC 29213) and C. albicans (ATCC 90028) up to a concentration of 50 μM. The average concentration derived from triplicates that exhibited a growth inhibition on visual inspection was considered as the Minimum Inhibitory Concentration (MIC). Moderate antimicrobial activity for peptide C was observed against S. aureus (MIC = 36.14 μM) and C. albicans (MIC = 18.07 μM). However, no inhibition was observed against E. coli up to the highest concentration tested. The human antimicrobial peptide LL 37 was used as the control (MIC value around 1-2 μM). The sequence analysis of the four peptides, their structural characterization and investigation of their potential applications are currently underway.
Microfractionation-based approach to screen potential specialized anti-microbial metabolites of Sri Lankan marine sponges
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Gamage, J.B.; Kosgahakumbura, L.N.; Cárdenas, P.; Jayasinghe, R.P.P.K.; Hettiarachchi, C.M.; Gunasekera, S.
The discovery of bioactive specialized metabolites from marine invertebrates has increased significantly during the last two decades. Marine sponges (phylum Porifera) are the existing oldest metazoan group that host rich microbial communities, and are considered as potential sources of future drugs in pharmacological and biomedical industry as they produce an impressive array of anti-inflammatory, immunosuppressive, neurosuppressive, antitumor, antiviral, and antimicrobial compounds. Of the few studies that have been carried out on such products in Sri Lankan marine sponges, the discovery of bioactive peptides has been largely overlooked. Therefore, a study was carried out to screen potential specialized anti-microbial metabolites especially peptides and sterols in Sri Lankan marine sponges with the intention of large scale isolation of targeted bioactive molecules. Bioassay-guided micro fractionation is an efficient method for the rapid screening of a large number of samples using only a small amount of starting material. Aqueous extracts (60% methanol) and organic extracts (Dichloromethane: methanol 9:1) of 20 different sponge species collected in coastal waters in Sri Lanka were micro fractionated into 48 fractions in deep well plates (1 mL per well), using reversed-phase HPLC. A volume of 100 µL from each fraction was tested for antimicrobial activities and the wells with antimicrobial activity were analyzed by LC-MS coupled to a PDA detector to identify the molecular ions of the bioactive compounds. Of all the 40 extracts, 18 extracts produced by Rhabdastrella globostellata, Aciculites sp., Rhabderemia sp., Erylus sp, Aulospongus sp., Manihinea sp., Agelas sp., Phakellia sp., Topsentia sp., four species belonging to order Haplosclerida and one species belonging to order Suberitida showed bioactivity against Staphylococcus aureus (ATCC 25928). Stylissa massa showed bioactivity against Escherichia coli (ATCC 35218) while Aulospongus sp., showed bioactivity against Candida albicans (ATCC 90028). Sponge species were identified using their morphology, spicule arrangement and DNA barcoding. The 5’ end of CO1 and 28S rRNA genes were sequenced for both forward and reverse direction. Sequences were compared using the BLASTn tool with the NCBI database in order to narrow down and identify the possible lowest taxonomic level. The wells that indicated bioactivity contained fractionated extract at ≤ 0.2 mg/mL concentration. Organic extracts of Aciculites sp., Topsentia sp. and the aqueous extract of Erylus sp. were the most active at ≤ 0.05 mg/mL. The targeted masses obtained from LC-MS will be isolated in large scale and the structural characterization of isolated specialized anti-microbial metabolites will be determined using LC-MS and NMR. Furthermore, these micro fractions will be subjected to lymphoma cell toxicity assay to identify potential anticancer compounds.
Neurophysiological findings in patients 1 year after snake bite induced neurotoxicity in Sri Lanka
(Oxford University Press, 2010) Bell, D.J.; Wijegunasinghe, D.; Samarakoon, S.; Palipana, H.; Gunasekera, S.; de Silva, H.A.; Lalloo, D.G.; Ranawaka, U.K.; de Silva, H.J.
Snake bite causes significant morbidity and mortality in Sri Lanka. Snake venoms contain neurotoxins that block neuromuscular junction transmission. Presynaptic neurotoxicity most commonly causes destruction of nerve terminals with recovery by regrowth, whilst postsynaptic neurotoxicity usually involves competition at the acetylcholine receptor. The aim of this study was to investigate whether there were long-term clinical or neurophysiological changes in snake bite survivors 1 year after their envenoming. Detailed neurophysiological tests and clinical examinations were performed on 26 snake bite victims who had presented with neurotoxicity 12 months previously, and their results were compared with controls recruited from the same communities. Significant differences were observed in some nerve conduction parameters in some snake bite victims compared with controls, predominantly in those thought to have elapid bites, including prolongation of sensory, motor and F-wave latencies and reduction of conduction velocities. There was no evidence of any residual deficits in neuromuscular junction transmission. These results suggest a possible demyelinating type polyneuropathy. None of the cases or controls had abnormalities on clinical examination. This is one of the few studies to report possible long-term neurological damage following systemic neurotoxicity after snake bite. The clinical significance of these neurophysiological abnormalities is uncertain and further studies are required to investigate whether the abnormalities persist and to see whether clinical consequences develop