Flight for fish in drug discovery: a review of zebrafish-based screening of molecules.

Human disease and biological practices are modelled in zebrafish (Danio rerio) at various phases of drug development as well as toxicity evaluation. The zebrafish is ideal for in vivo pathological research and high-resolution investigation of disease progress. Zebrafish has an advantage over other mammalian models, it is cost-effective, it has external development and embryo transparency, easy to apply genetic manipulations, and open to both forward and reverse genetic techniques. Drug screening in zebrafish is suitable for target identification, illness modelling, high-throughput screening of compounds for inhibition or prevention of disease phenotypes and developing new drugs. Several drugs that have recently entered the clinic or clinical trials have their origins in zebrafish. The sophisticated screening methods used in zebrafish models are expected to play a significant role in advancing drug development programmes. This review highlights the current developments in drug discovery processes, including understanding the action of drugs in the context of disease and screening novel candidates in neurological diseases, cardiovascular diseases, glomerulopathies and cancer. Additionally, it summarizes the current techniques and approaches for the selection of small molecules and current technical limitations on the execution of zebrafish drug screening tests.

Histopathological and Biochemical Changes in the Gills of Anabas testudineus on Exposure to Polycyclic Aromatic Hydrocarbon Naphthalene.

Naphthalene, a polycyclic aromatic hydrocarbon, is generated by various distillation, petroleum, and coal-tar production units and is used worldwide as mothballs, soil fumigants, and toilet deodorants. Considering the susceptibility of aquatic animals to different types of stressors in several water bodies, this study was carried out to evaluate the impact of naphthalene on the architecture of gill tissue including response of various enzymes like cholinesterase (ChE) activity, lactate dehydrogenase (LDH) activity, and lipid peroxidation (LPX) level of the freshwater fish Anabas testudineus. Activities of antioxidants like catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) were also evaluated. Constant loss of gill structure and secondary lamellar fusion was observed in fishes exposed to various concentrations of naphthalene. ChE, LDH, LPx, CAT, Gpx and GSH activities indicated significant variation (p < 0.05) between the control and experimental groups. ChE activity was lowered in experimental fishes; however, LDH activity, LPx levels, and CAT activity were elevated in response to various concentrations of naphthalene as compared to control group. Both GPx and GSH activities decreased in the gill tissue of the experimental fishes. Thus, a conclusion was drawn that naphthalene is a potent toxicant capable of inflicting tissue damage leading to physiological changes in the exposed fishes.

Role of Integrated Biomarker Response Tool for Assessment of Naphthalene Toxicity in Anabas testudineus.

Polyaromatic hydrocarbons are highly stable and can easily permeate through biological membranes due to their lipophilic nature. They are characterized by their ability to act at the site of application and even at sites distant to the zone of application. Any contamination associated with aquatic bodies due to the presence of PAHs can be assessed by investigating biochemical changes. The most common polycyclic aromatic hydrocarbon (PAH) pollutant naphthalene was selected for the bioassay experiment using Indian climbing perch Anabas testudineus. The biochemical response in the muscle tissue was investigated after exposure to varying concentrations of naphthalene by estimating protein, glycogen, Alanine Aminotransaminase, and Aspartate Aminotransaminase. The results showed inhibition of protein and glycogen levels due to naphthalene stress. Similarly, a decrease in the activity of transaminase in muscle tissues was noticed. The results have been computed using star plots for interpretation of integrated biomarker response (IBR). The results clearly support the role of biochemical parameters in assessing the impact of naphthalene stress on fish health. IBR index can be developed as a useful tool in monitoring quantitative as well as the qualitative effect of naphthalene toxicity in fishes and other aquatic animals.

Species composition of microzooplankton Tintinnid from the coastal waters of Digha, Bay of Bengal.

Tintinnid species distribution and hydrography were studied in the coastal waters of Digha during winter (November 2015) and summer (March 2016) seasons. Surface water samples were collected from 11 different stations from 0 to 10 km offshore with the help of a mechanized trawler. Parameters like tintinnid species enumeration, zooplankton biomass, phytoplankton concentration (total chlorophyll) and abundance, sea surface temperature (SST), pH, transparency, salinity, dissolved oxygen (DO), total phosphate, silicate and nitrate were analysed. A total of 20 different tintinnid species (16 agglomerated +4 non-agglomerated) belonging to 6 genera were recorded from the study area with seasonal variation in tintinnid diversity, i.e. higher in summer (total 2745 individual/l) compared to winter (total 1191 individual/l). Tintinnopsis was the most dominant genus during both the seasons, i.e. 2100 individual/l in summer and 727 individual/l in winter, contributing about 76 and 61% population for the respective seasons. The correlation between species and water quality parameters showed that Tintinnopsis sp. abundance was significantly regulated by nitrate concentration, salinity, dissolved oxygen, water transparency and pH. However, the mentioned hydrological parameters were not the only factors regulating the tintinnid abundance. Tintinnid abundance was also found to be positively related with transparency (r = 0.732) and salinity (r = 0.524) and moderately related with dissolved oxygen (r = 0.488) whereas strong negative relation (at p ≤ 0.05) was established between tintinnid abundance with nitrate (r = -0.681) and pH (r = -0.561). Bray-Curtis cluster analysis of tintinnid species showed more than 60% similarity. Shannon's diversity index (H'), Simpson's evenness index (D) and Margalef's species richness index were found to be higher in summer, i.e. 1.61, 0.729 and 1.612, compared to the winter season, i.e. 1.139, 0.597 and 1.268. k-dominance curve showed maximum abundance of Tintinnopsis baltica in winter and Tintinnopsis gracilis in summer. Principal component analysis (PCA) was analysed to find out the environmental variables affecting different tintinnid species diversity. A significant spatiotemporal variation in Tintinnid population distribution was observed from two-way ANOVA. The results reflect significant seasonal (F = 840.0), spatial (F = 47.3) and interactive variation (F = 71.2) among the ciliate microzooplankton at n = 66, p ≤ 0.001. High chlorophyll content and phytoplankton population in summer indicated that tintinnid diversity in the season was positively influenced by producer community in coastal waters of Digha.