Microcystin-LR (MC-LR) is a potent hepatotoxin, and increasing evidence suggests that it might also induce kidney injury. The aim of the present work was to evaluate the cytotoxicity and possible apoptotic effects of MC-LR on a human embryonic kidney cell line (HEK-293) and human kidney adenocarcinoma cell line (ACHN). Cells were exposed for 24 h to pure MC-LR (1.0-200 mM) and the cytotoxic effects were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and sulphorhodamine B (SRB) cell viability assays. Cell viability in both cell lines was significantly decreased after treatment with MC-LR at 50 mM for 24 h (P,0.001). Moreover, MC-LR-treated ACHN and HEK-293 cells exhibited a marked dosedependent loss of confluence as judged by phase-contrast microscopy. Similarly, fluorescence microscopic observations following acridine orange-ethidium bromide (AO/EB) staining confirmed that both cell types were undergoing apoptosis after treatment with MC-LR for 24 h. Expression of three apoptosis-related genes, Bax, Survivin and p53, was analysed by quantitative reverse transcriptase PCR analysis. Both Bax and p53 functioned as promoters of MC-LRmediated apoptosis in ACHN and HEK-293 cells. The Survivin gene acted as a suppressor of apoptosis at lower MC-LR concentration (1 mM) and the gene was upregulated at higher MC-LR concentration (10 mM) (P,0.001). Significant increases of caspase 3 (P,0.0001) and caspase 9 (P,0.0001) activity were detected in both cell lines after exposure to MC-LR for 24 h, indicating the MC-LR induces cytotoxicity and a marked apoptosis in both ACHN and HEK-293 kidney cell lines.

Abstract:To intensify the production of edible oyster in Sri Lanka in the future it is essential to analyse the status of the present culture practices. The present study was carried out to investigate the growth and health of cultured edible oyster, Crassostrea madrasensis in relation to the prevailing water quality parameters and external fouling in a small-scale, commercial farm located in the Panadura estuary, Sri Lanka.The mean growth rate in shell length and shell width varied between 0.06 ± 0.01 mm and 2.19 ± 0.09 mm and between 0.02 ± 0.02 and 2.11 ± 0.39 mm per week, respectively. There were positive significant relationships between the growth rate in shell width and salinity, as well as the conductivity of culture water (p < 0.05). Mean total dissolved solids in culture water had a positive significant relationship to the growth rate of oysters in shell length (p < 0.05). External fouling organisms that grew on the outer shell surface caused significant reduction in growth rate as well as the weight gain of cultured C. madrasensis (p < 0.05).Histological sections of the gills, mantle, digestive gland and digestive tract of oysters exhibited structures similar to plasmodia of a haplosporidian parasite, which reached the stage of rupturing during the period of low salinity. C. madrasensis could tolerate the low salinity, ranging from 0 gL -1 to 6.0 gL -1 with 83.0 ± 2.47 % survival; the highest mortality recorded during the period with low salinity in culture water was 15.00 ± 2.50 %.

Freshwater cyanobacterial blooms limit the utilization of drinking water due to decreased clarity, bad odor, anoxia in the water column and producing a diverse range of toxins; hepatotoxins, neurotoxins and cytotoxins. Hepatotoxic microcystin-LR (MC-LR) is the most intensively studied cyanotoxin and it is the most common type of cyanotoxin. The present study was based on qualitative and quantitative analysis of cyanotoxin in diverse water bodies in Sri Lanka and thirty one water bodies in different districts of Sri Lanka were selected for qualitative and quantitative analysis of microcystin-LR using PCR and ELISA techniques respectively along with assessment of some other selected physico-chemical water quality parameters. Presence of MCs producing genes, mcy A, mcy B and mcy E in field samples were analysed by PCR using specific primers and quantification of Microcystin-LR was done by Enzyme Link Immuno Sorbent Assay (ELISA) respectively. The results of the present study relvealed that most of the drinking water reservoirs were having acceptable physico-chemical parameters for drinking water and MC-LR contamination was ranged between 5.98 ppb to 0.03 ppb. The highest contamination of MC-LR was recorded in Giradurukotte Reservoir (435ppb) where moderate level of MC-LR was detected in Kurunagala lake (75.6 ppb). PCR results reveled that most of studied water bodies having MCs producing genes, mcy A, mcy B and mcy E except Labugama reservoir, Kalatuwawa reservoir, Rathkinda reservoirs, Kantale podi wewa, Minneriya wewa and Mahaweli river intake. Thus, PCR screening is a cost effective molecular biological tool to detect cyanotoxin contamination status of a water body in adavance and it may facilitate to future forcast for actual potential of cyanotoxins production and give an alarm to take nessaary treatment application for drinking water supply authorities.