Molecular and biochemical responses to tributyltin (TBT) exposure in the American oyster: Triggers of stress-induced oxidative DNA damage and prooxidant-antioxidant imbalance in tissues by TBT

Environmental pollution increases due to anthropogenic activities. Toxic chemicals in the environment affect the health of aquatic organisms. Tributyltin (TBT) is a toxic chemical widely used as an antifouling paint on boats, hulls, and ships. The toxic effect of TBT is well documented in aquatic organisms; however, little is known about the effects of TBT on DNA lesions in shellfish. The American oyster (Crassostrea virginica, an edible and commercially important species) is an ideal marine mollusk to examine the effects of TBT exposure on DNA lesions and oxidative/nitrative stress. In this study, we investigated the effects of TBT on 8'-hydroxy-2'-deoxyguanosine (8-OHdG, a biomarker of pro-mutagenic DNA lesion), double-stranded DNA (dsDNA), dinitrophenyl protein (DNP, a biomarker on reactive oxygen species, ROS), 3-nitrotyrosine protein (NTP, a biomarker of reactive nitrogen species, RNS), catalase (CAT, an antioxidant), and acetylcholinesterase (AChE, a cholinergic enzyme) expressions in the gills and digestive glands of oysters. We also analyzed extrapallial (EF) fluid conditions. Immunohistochemical and qRT-PCR results showed that TBT exposure significantly increased 8-OHdG, dsDNA, DNP, NTP, and CAT mRNA and/or protein expressions in the gills and digestive glands. However, AChE mRNA and protein expressions, and EP fluid pH and protein concentrations were decreased in TBT-exposed oysters. Taken together, these results suggest that antifouling biocide-induced production of ROS/RNS results in DNA damage, which may lead to decreased cellular functions in oysters. To the best of our knowledge, the present study provides the first molecular/biochemical evidence that TBT exposure results in oxidative/nitrative stress and DNA lesions in oysters.

The reproductive biology of flesh fly, Boettcherisca peregrina (Robineau-Desvoidy, 1830) (Diptera: Sarcophagidae)

The reproductive biology of the flesh fly, Boettcherisca peregrina (Diptera : Sarcophagidae ) was studied in the blowfly laboratory (25 -30ºC, 60 - 80% RH and 12 hrs light and 12 hrs dark) of the Institute of Food and Radiation Biology, Atomic Energy Research Establishment, Dhaka. The female reproductive system of B. peregrina comprises of two ovaries, two lateral oviducts, a common oviduct, three spermathecae, and a pair of accessory gland, a bilobed incubation pouch, vagina and genital opening. The male reproductive system B. peregrina consists of a pair of testes, a pair of vasa deferentia, a pair of accessory gland, a median ejaculatory duct, an ejaculatory sac and aedeagus. There is a general trend of gradual development of different organelles of the male and female reproductive systems from adult emergence to reproductive maturity. Protein diet was essential for proper development of female reproductive system. Oocyte development was apparent in both protein fed and protein unfed females. The mean sex-ratio of male to female was 20.2 : 14.2.  

The biology of flesh fly, Boettcherisca peregrina (Robineau-Desvoidy, 1830) (Diptera: Sarcophagidae)

The biology of Boettcherisca peregrina (Robineau-Desvoidy, 1830) (Diptera: Sarcophagidae) was studied in the laboratory (25 ± 5ºC, R.H. 70 ± 10% and 12 h light: 12 h dark cycle ). There were four definite life stages, such as egg, larva, pupa and adult, in its life cycle. The mean duration of the life cycle was 13.19 ± 1.32 days. The egg was creamy white color, cylindrical, rounded at both ends. The egg shell was comparatively thick and hard. There were three larval instars. The larvae of B. peregrina were acephalous and apodus type. The transparent 12 segmented larva possessed a pair of mouth hook, bands of small backwardly directed black micro spines, a pair of prothorasic spiracle and a pair of posterior spiracle. The 1st larvae were relatively more transparent at the time of hatching. The second instar larvae were voracious feeder. The body size increased largely during the third instar. They were deep creamy to pale brownish in color. The pupae of B. peregrina were coarctate adecticous type. The posterior end of the puparium was rounded and the anterior end was slightly pointed. The adults were metallic brown in color. The males were smaller in size than the females. The mean incubation period was 11.6 ± 2.70 hours, and the larval, post-feeding and pupal periods were 102.22 ± 7.85 hours, 75.4 ± 3.57 hours, and 5.81 ± 1.30 days, respectively. The longevity of the mated male and female adults (36.9 ± 2.46 days and 27.2 ± 2.25 days, respectively) were more than that of the unmated ones (23.6 ± 2.25 days and 18.3 ± 1.5 days, respectively). The protein fed adults lived longer than the protein unfed ones.The male always lived longer than the female. DOI: http://dx.doi.org/10.3329/bjz.v40i2.14312 Bangladesh J. Zool. 40(2): 189-196, 2012

Flocculation properties of polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) synthesised by conventional and microwave assisted method

A novel polymeric flocculant based on polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) has been synthesised by grafting polyacrylamide chains onto CMG backbone using conventional redox grafting and microwave assisted grafting methods. Under optimum grafting conditions, 82% and 96% grafting efficiencies have been observed in case of conventional and microwave assisted methods respectively. The optimum sample has been characterized using viscometry, spectroscopic analysis, elemental analysis, molecular weight and radius of gyration determination. The flocculation characteristics of grafted and ungrafted polysaccharides have been evaluated in kaolin suspension, municipal sewage wastewater and decolourization efficiency of a dye solution (methylene blue). It is evident from results that CMG-g-PAM synthesised by microwave assisted grafting method is showing best flocculation characteristics.