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@#Introduction: Inhibition of the cholinesterase’s function leads to paralysis and death. This mechanism is served as a common mode of action of insecticide. The three tropical seaweeds, namely Bryopsis pennata, Padina australis and Sargassum binderi were reported for its potential mosquito larvicidal effect. In the present study, these seaweeds were evaluated for their potential as a cholinesterase inhibitor in the mechanism of larvicidal action. Methods: Acetylcholinsterase (AChE) inhibition assay was carried out based on the colorimetric method using a microplate reader. Phytochemical content of the seaweed extracts was screened by using liquid chromatography-mass spectroscopy (LC-MS). Results: Green seaweed B. pennata showed the strongest inhibition effect towards in vitro AChE by using tissue homogenates of Aedes aegypti (IC50 value = 0.84 mg mL-1) and Aedes albopictus as the enzyme source (IC50 value = 0.92 mg mL-1). The pattern of Lineweaver-Burk plots revealed that B. pennata was a mixed type inhibitor of AChE, as the readings of Km, Vmax, Ki and Ki’, indicates that it had a strong inhibition ability with high binding affinity towards both free enzyme and enzyme-substrate complex. Conclusion: These findings suggest the compound(s) in B. pennata extract serves as a promising source that could be developed into a mosquito larvicidal agent with AChE inhibition effect.
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Objective: To assess the insecticide susceptibility status of Anopheles cracens (An. cracens) and Anopheles maculatus (An. maculatus) from knowlesi malaria endemic areas in Peninsular Malaysia towards DDT, malathion and deltamethrin and to determine the resistance mechanism involved. Methods: Adult and larval mosquitos were collected for surveillance. Susceptibility status of Anopheles was determined using the standard WHO adult bioassay, larval bioassay and biochemical enzyme assay. Results: WHO adult bioassay results indicated An. cracens collected from Kampung Sungai Ular, Pahang was resistant towards 4% DDT, while An. maculatus collected from Kampung Sokor, Kelantan and Kampung Sungai Lui, Selangor exhibited resistance towards 4% DDT. However, the enzyme activity profiles varied according to strains and species. The resistance ratio of larval bioassay, showed that all strains and species tested were susceptible to malathion and temephos. Conclusions: Since only a few anopheline strains exhibited low level of insecticide resistance towards malathion, DDT and temephos. These insecticides are still considered effective for vector control program towards An. cracens and An. maculatus.
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·AIM: To study the mechanism and effect of Qingxuan decoction on evaporative dry eye in rabbit model. ·METHODS: Totally 25 healthy male Japanese white rabbits were randomly divided into 5 groups: control group, model group, western medicine group, high dose of Qingxuan decoction group, low dose of Qingxuan decoction group. The blank control group did not do any treatment. The improved dry eye model of rabbit was prepared by the improved method of glandular burning of the eyelid plate. The high and low dose group were given daily 27. 2mg/kg, 6. 8mg/kg Qingxuan decoction by gavage. The model group was intragastric with the same amount of normal saline every day. The western medicine group with tobramycin and dexamethasone ophthalmic ointment 1 drops, once a day. The treatment were administered continuously for 28d. At 14d before the experiment, 7d before the experiment, 7d after the model, and 14d after the model, all the rabbits were tested by Schirmer Ⅰ test ( SⅠt) and break-up time (BUT). On the 15d after modeling, the animals were sacrificed by excessive anaesthesia. Rabbit ocular surface tissue sections were prepared. Hematoxylin - eosin staining method was used to observe the corneal morphological changes in each group. The concentrations of TNF-α, IL-1 and IL-6 in the ocular surface of rabbits were detected by ELISA. ·RESULTS: (1) BUT, SⅠt: 7d after the model had been prepared, BUT and SⅠt of the model group and the western medicine group, high dose and low dose of Qingxuan decoction group was improved ( P< 0. 05 );Those of western medicine group, high dose and low dose of Qingxuan Decoction group compared with the model group, were significantly different (P<0. 05). (2) TNF-α, IL-1, IL-6: The ELISA assay showed that TNF-α and IL-1, IL-6 concentration in the model group rabbits was significantly higher than those of the control group, TNF-α and IL-1, IL-6 concentration in western medicine group and high dose group of rabbits was significantly lower than those in the model group, the differences were statistically significant (P<0. 05), and in high dose group the effect was better than that of Western medicine group. ( 3 ) Histopathological examination: on the 14d after the model, the corneal epithelium in the blank control group was stratified well. The cells in the base were columnar, near the surface, the cornea epithelium showed a squamous change. Conjunctiva showed complete epithelial layer and subconjunctival tissue layer, and goblet cells arranged closely. The number of corneal epithelial cells in model group was reduced or even stripped, and the matrix layer was disorder; Irregular loss of conjunctival epithelial cell layer and a large decrease in goblet cells. The corneal morphology of the rabbits in the western medicine group and the high dose group was close to the normal group, and the number of conjunctival goblet cells was not significantly different from that in the blank control group. ·CONCLUSION: The expression of Qingxuan decoction can inhibit the inflammatory reaction through down -regulation of TNF-α and IL-1, IL-6 and in evaporative dry eye rabbit cornea and conjunctiva, so as to improve the ocular symptoms, increase tear secretion, prolong the time of BUT.
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OBJECTIVE@#To investigate the larvicidal activity, inhibition effect on development, histopathological alteration and morphological aberration induced by the extracts derived from seaweeds Bryopsis pennata (B. pennata), Sargassum binderi (S. binderi) and Padina australis in Aedes aegypti (Ae. aegypti) larvae and to characterize the phytochemical components of the three seaweeds.@*METHODS@#Larvicidal activity of the seaweeds towards the larvae of Ae. aegypti was determined according to WHO. The inhibition effect of seaweeds was assessed by determining the mortality, adult emergence rate, larval and pupa duration of the treated larvae. Histopathological effect on midgut epithelium of larvae and morphological aberration induced by the methanol extracts were examined. Phytochemical analysis was done to determine the presence of alkaloids, saponins, steroids and terpenoids in the seaweeds.@*RESULTS@#Chloroform partition of B. pennata extract exhibited the strongest larvicidal activity (LC50 = 82.55 μg/mL), followed by methanol extract of B. pennata (LC50 = 160.07 μg/mL) and chloroform partition of S. binderi extract (LC50 = 192.43 μg/mL). The methanol extract of S. binderi exhibited the strongest effect on prolongation of larval period (1.5-fold longer as compared to control) and resulted in strongest inhibition effect in adult emergence (98.67%). The histopathological study showed that larvae treated with seaweed extracts had cytopathological alteration of the midgut epithelium. The morphological observation revealed that the anal papillae and terminal spiracles of larvae were the common sites of aberrations.@*CONCLUSIONS@#The study provided information on various effects of seaweed extracts on Ae. aegypti. Further investigation on identifying the active compounds and their mechanisms of action is recommended.
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Objective: To investigate the larvicidal activity, inhibition effect on development, histopathological alteration and morphological aberration induced by the extracts derived from seaweeds Bryopsis pennata (B. pennata). Sargassum binderi (S. binderi) and Padina australis in Aedes aegypti (Ae. aegypti) larvae and to characterize the phytochemical components of the three seaweeds. Methods: Larvicidal activity of the seaweeds towards the larvae of Ae. aegypti was determined according to WHO. The inhibition effect of seaweeds was assessed by determining the mortality, adult emergence rate, larval and pupa duration of the treated larvae. Histopathological effect on midgut epithelium of larvae and morphological aberration induced by the methanol extracts were examined. Phytochemical analysis was done to determine the presence of alkaloids, saponins, steroids and terpenoids in the seaweeds. Results: Chloroform partition of B. pennata extract exhibited the strongest larvicidal activity (LC