Ayanthi Navaratne

Chemical Characterization of Gallstones: An Approach to Explore the Aetiopathogenesis of Gallstone Disease in Sri Lanka

Introduction Records on gallstones and associated ailments in Sri Lankan community are scarce, despite frequent detection of gallstone disease. Identification of the chemical composition of gallstones in the local setting is important in defining aetiopathogenic factors which in turn are useful in implementing therapeutic and preventive strategies. This study aimed to describe the chemical composition of gallstones and the socio-demographic factors of a cohort of Sri Lankan patients with gallstone disease. Materials and Methods Data on clinical and socio-demographic factors, and gallstones removed at surgery were collected from patients with cholelithiasis admitted to Teaching Hospital, Peradeniya, Sri Lanka from May 2011 to December 2012. External and cross sectional morphological features of gallstones were recorded by naked eye observation. Compositional analysis was carried out by Fourier Transform Infrared Spectroscopy, X - ray Powder Diffraction, and Atomic Absorption Spectrophotometry. Scanning Electron Microscopy was used to identify the microstructure of gallstones. Results Data of 102 patients were analyzed. Of them majority (n = 77, 76%) were females with a female: male ratio of 3:1. Mean age of the study group was 46.1±11.6 years. All the patients had primary gallbladder stones. According to the physical and chemical analysis, majority (n = 54, 53%) were pigment gallstones followed by mixed cholesterol gallstones (n = 38, 37%). Only 10 (9%) had pure cholesterol gallstones. Calcium bilirubinate, calcium carbonate and calcium phosphate were the commonest calcium salts identified in pigment gallstones and core of mixed cholesterol gallstones. Conclusion Presence of a pigment nidus in gallstones is a common feature in majority of Sri Lankan patients denoting the possible role of elevated unconjugated bilirubin in bile on the pathogenesis of GS. Hence it is imperative to explore this further to understand the aetiopathogenesis of GS among Sri Lankans.

Malformations and mortality in the Asian Common Toad induced by exposure to pleurolophocercous cercariae (Trematoda: Cryptogonimidae).

Malformations and increased mortality due to infection by the digenetic trematode, Riberioa ondatrae have been reported for many species of amphibians. Severe malformations have also been reported in the Common Hourglass Tree Frog, Polypedates cruciger induced by pleurolophocercous cercariae in Sri Lanka in addition to the changes in the behaviour, development and survival of the host. We exposed pre-limb bud stage tadpoles (Gosner stages 25-26) of the Asian Common Toad, Duttaphrynus melanostictus to the same pleurolophocercous type cercariae under laboratory conditions. Molecular and morphological identification showed that these cercariae belonged Acanthostomum burminis infecting freshwater snakes as definitive hosts. These cercariae induced malformations (27.8%) and reduced survival to metamorphosis (53.8%). The magnitude of the effects increased with the dose of cercariae. Types of malformations were mainly axial, such as scoliosis and kyphosis. Severe limb malformations such as extra or missing limbs as reported for amphibians exposed to R. ondatrae were not observed in the D. melanostictus. Same authors reported a higher percentage of malformations previously when P. cruciger was exposed to the cercariae A. burminis compared to D. melanostictus. However, tadpoles of D. melanostictus, which are smaller compared to those of P. cruciger, experienced higher mortality than P. cruciger tadpoles. Trematode induced malformations and mortality in amphibians are highly variable and depend on multiple factors such as host species differences such as resistance to infection and tolerance, life-history characteristics such as size at metamorphosis and length of the metamorphosis period, and other factors such as size of the amphibian at the time of trematode exposure.

Solvent extraction followed by ultraviolet detection for investigation of tetramethylthiuram disulfide at soil-water interface

Tetramethylthiuram disulfide is a widely used pesticide and a soil treatment agent in the agricultural sector. Consequently, its detection in the environment and investigation of the distribution between the aqueous and soil phases would be of highly importance. In this study, the detection of tetramethylthiuram disulfide in CHCl3 was successfully achieved through absorbance measurements at 280 nm, which resulted in linear calibration curves. This detection method was extended for the determination of the partition coefficient (KD) of tetramethylthiuram disulfide between CHCl3 and H2O phases at ambient temperature. The partition coefficient was subsequently used to determine the apparent partition coefficient (KD) of tetramethylthiuram disulfide between sieved soil of diamater < 2.0 mm used for agricultural practices and water where by the quantification of tetramethylthiuram disulfide in water after adsorption equilibrium with soil was achieved through a solvent extraction step of tetramethylthiuram disulfide-contaminated water into CHCl3. The KD determined for an initial tetramethylthiuram disulfide concentration ranging from 3.00 ppm to 10.00 ppm showed a decreasing trend, which leveled off at high concentrations, indicating the strong irreversible adsorption behavior of tetramethylthiuram disulfide on soil at low concentrations. The proposed detection method would have the potential to determine the extent of adsorption of tetramethylthiuram disulfide in soil or its levels in water when tetramethylthiuram disulfide is introduced to soil systems for agricultural practices.

Chemically Modified Electrodes for Detection of Pesticides

Environmental problems and their control have received a great deal of interest and publicity, and the number of pesticides used in agriculture and other applications has been steadily increasing. Environmental scientists are concerned with reliable means for detecting these compounds. Although many advances have been made in this area in recent years, much is yet to be accomplished. Chemistry plays a vital role in environmental protection, and analytical chemistry must meet the challenge of providing qualitative as well as quantitative characterization of pesticides. It has already been warned that some organic and inorganic compounds have harmful effects at substantially lower levels than previously suspected (1). Thus, there is a great necessity for new analytical methods with better precision, accuracy, sensitivity and selectivity. These methods must not be prohibitively expensive and, ideally, could be adapted for measurement in the field. Existing analytical techniques have limitations when used for environmental monitoring. Xray and electron diffraction, mass spectrometry, activation analysis, and spectral laser methods are not only sophisticated and expensive, but also require specially trained personnel for proper operation of instrumentation. Although gas-liquid chromatography (GLC or GC) has been used with its variety of sensitive and selective detectors, the technique is limited to volatile compounds (2). Non-volatile compounds are commonly derivatized prior to gas chromatographic detection to increase their volatility. High performance liquid chromatography (HPLC) is useful for non-volatile samples (3), but commercially available detectors are limited in sensitivity and/or selectivity. A variety of electroanalytical methods have been widely employed for detection of pesticides at bare electrodes (4-7). Drawbacks of bare electrodes have been overcome by the use of electrodes whose surfaces are modified with specific functionalities (chemically modified electrodes or CMEs). This paper summarizes analytical capabilities of electrochemistry for detecting pesticides in the environment. The discussion will be mainly focused on electrochemical detection of pesticides at metalloporphyrin modified electrodes (MPEs). An introduction to CMEs and metalloporphyrin electrochemistry will also be included. Furthermore, the application of modified electrodes for detection of pesticides and the suitability of electrochemistry in conjunction with liquid chromatography (LCEC) for separation of environmental samples followed by detection of pesticides will be discussed.