Metaldehyde is used widely in Malaysia for the control of molluscs. This communication reports the cytotoxic effects of this chemical on cultured cells as assessed by cell morphology and the DNA synthesising capability as well as its transport into cells. After 15 days of exposure with 20.0 ppm of the compound, the DNA synthesising capability was shown to be unaffected. The IC50 for Vero cells was 276.0 ppm. Transport of thymidine across cells was found to be not significantly affected even at high metaldehyde concentrations (up to 320.0 ppm) suggesting integrity of cells were not significantly affected. The present cellular studies have therefore shown that the cytotoxic effects of this chemical is rather low.
Metaldehida digunakan dengan meluas di Malaysia untuk mengawal perosak moluska. Kesan sitotoksik bahan kimia ini di peringkat sel dari segi ciri-ciri perubahan moifologi dan keupayaan mensintesis DNA serta kajian awal kesannya terhadap proses kemasukan ke dalam sel dilaporkan di sini. Keupayaan mensintesis DNA didapati tidak terjejas secara signifikan selepas diberikan 20.0 ppm metaldehida secara berterusan selama 15 hari. Nilai IC50 bagi sel Vero adalah 276.0 ppm. Kemasukan timidina ke dalam sel tidak terjejas secara signifikan apabila sel diperlakukan dengan metaldehida, walaupun pada kepekatan yang agak tinggi iaitu sehingga 320.0 ppm. Kajian telah menunjukkan bahawa kesan sitotoksik oleh metaldehida adalah rendah.
The influence of temperature, moisture and organic matter on the persistence of cyfluthrin was determined using three types of Malaysian soils, namely clay, clay loam and sandy clay loam obtained from a tomato farm in Cameron Highlands, Pahang. The persistence of cyfluthrin was observed in the laboratory at two temperature levels of 25 and 35 degreeC and field water capacity of 30 and 80%. Treated soil samples were incubated in a growth chamber for 1, 2, 3, 5, 7, 10, 14, 21 and 28 days. The results from the incubation studies showed that temperature and organic matter content significantly reduced the half-life (t1/2) values of cyfluthrin in the three soil types, but moisture content had very little effect. It was observed that cyfluthrin persisted longer at lower temperature and moisture content and higher organic matter content in all the three soil types. The present study demonstrated that under the tropical conditions of Malaysia, cyfluthrin dissipated rapidly in soils compared to its dissipation in soils of temperate regions, evidently due to high temperature.
This paper reports the sorption of three metallic ions, namely Cr(VI), Cu(II) and Pb(II) in aqueous solution by a consortium culture (CC) comprising an acclimatised mixed bacterial culture collected from point and non-point sources. Metal sorption capability of growing and non-growing cells at initial pH of between 3 and 8 in the 1-100mg/L concentration range were studied based on Q(max) and K(f) values of the Langmuir and linearised Freundlich isotherm models, respectively. Maximal metal loading was generally observed to be dependent on the initial pH. Growing cells displayed significant maximal loading (Q(max)) for Pb(II) (238.09 mg/g) and Cu(II) (178.87 mg/g) at pH 6 and at pH 7 for Cr(VI) (90.91 mg/g) compared to non-growing cells (p < 0.05). At the pH range of 6-8, growing cells showed higher loading capacity compared to non-growing cells i.e. 38-52% for Cr, 17-28% for Cu and 3-17% for Pb. At lower metal concentrations and at more acidic pH (3-4) however, non-growing cells had higher metal loading capacity than growing cells. The metal sorption capacity for both populations were as follows: Pb(II) > Cu(II) > Cr(VI).
The relationship between a putative metallothionein gene (MT) and exposure to cadmium (Cd) in blood cockles (Anadara granosa) is reported. In a 96-h dose-response experiment, mortality of cockles was found to proportionately increase in the range of 0.2-5.0 mg/l Cd with a calculated LC(50) of 2.94 mg/l. Exposure to 0.25 mg/l Cd for 16 days caused significant increases (P<0.05) in Cd concentrations in whole tissues, gills and hepatopancreas, and the accumulation of Cd in these tissues increased with the duration of exposure. Two cDNA libraries constructed using the hepatopancreas from control and Cd-treated cockles gave titres of 5.62 x 10(5) and 1.94 x 10(5) pfu/microg vector, respectively. A putative MT gene, AnaMT, of 510 nucleotides in length, was isolated from the treated cDNA library using a heterologous probe MT20 from the blue mussel, Mytilus edulis. Northern analyses using AnaMT as a probe indicated low expression of the MT mRNA in control animals. In cockles treated with 0.25 mg/l Cd for 4 days, MT mRNA level increased to approximately 168%, but declined to 108% at day 8. After 12 and 16 days of Cd treatment, expression of the MT gene was 138% and 187%, respectively, compared to the controls. These observations suggest that induction of the MT gene by a sublethal dose of Cd is rapid, occurring within 4 days of treatment.
This study reports the results of the partial DNA sequence analysis of the 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS) gene in glyphosate-resistant (R) and glyphosate-susceptible (S) biotypes of Eleusine indica (L.) Gaertn from Peninsular Malaysia. Sequencing results revealed point mutation at nucleotide position 875 in the R biotypes of Bidor, Chaah and Temerloh. In the Chaah R population, substitution of cytosine (C) to adenine (A) resulted in the change of threonine (Thr106) to proline (Pro106) and from C to thymidine (T) in the Bidor R population, leading to serine (Ser106) from Pro106. As for the Temerloh R, C was substituted by T resulting in the change of Pro106 to Ser106. A new mutation previously undetected in the Temerloh R was revealed with C being substituted with A, resulting in the change of Pro106 to Thr106 indicating multiple founding events rather than to the spread of a single resistant allele. There was no point mutation recorded at nucleotide position 875 previously demonstrated to play a pivotal role in conferring glyphosate resistance to E. indica for the Lenggeng, Kuala Selangor, Melaka R populations. Thus, there may be another resistance mechanism yet undiscovered in the resistant Lenggeng, Kuala Selangor and Melaka populations.
The sorption and desorption of cyfluthrin mixture isomers were determined using batch equilibration method and mobility was studied under laboratory conditions, using packed soil column. The soil types used in the study were clayey, clay loam and sandy clay loam obtained from three tomato farms in Cameron Highlands. A low Freundlich adsorption distribution coefficient K(ads(f)) for cyfluthrin was observed for clayey, clay loam and sandy clay loam soils (95.69, 21.64 and 8.99 l/kg, respectively). Results showed that cyfluthrin had high Freundlich organic matter (OM) distribution coefficient K(oc) values of 5799, 2278 and 1635 lkg(-1) for clayey, clay loam and sandy clay loam soils, respectively. These values indicate that cyfluthrin is considered immobile in Malaysian soils with different textures, based on the value of K(oc) by McCall. Adsorption of cyfluthrin was significantly (P < 0.05) affected with soil pH, fertilizer NPK, organic matter content and temperature. It was observed that approximately 95.8%, 93.8% and 91.8% of the adsorbed cyfluthrin remained sorbed after four successive rinses for clayey, clay loam and sandy clay loam soils. Soil column test showed that cyfluthrin was not detected in leachate. Cyfluthrin was detected in topsoil and its concentration decreased with depth. The downward movement of cyfluthrin in sandy clay loam soil was more than that in clay loam and clayey soils. Approximately, 80.9%, 77.8% and 67.3% cyfluthrin was observed at the depth of 0-5 cm (rainfall 350 mm) for clayey, clay loam and sandy clay loam soils respectively. Mobility of cyfluthrin showed that the percentage of cyfluthrin leached into soil was not affected by the amount of rainfall. The result clearly showed that cyfluthrin molecules were bound strongly to all the three Malaysian soil types.