Alterations in the oxidative metabolism of Rhipicephalus (Boophilus) microplus ticks in response to exposure to the insect growth regulator fluazuron / Alterações no metabolismo oxidativo de carrapatos Rhipicephalus (Boophilus) microplus em resposta à exposição ao regulador de crescimento fluazuron

Abstract Aiming to characterize the potential off-target effects of fluazuron on ticks, biochemical analyses were conducted to evaluate changes in the carbohydrate metabolism of Rhipicephalus (Boophilus) microplus ticks after exposure to fluazuron. Hemolymph and fat body were collected from female ticks before and after (4, 8 and 15 days) exposure to fluazuron. Spectrophotometric analyses were done to quantify glucose concentration and lactate dehydrogenase (LDH) activity in the hemolymph and the concentration of glycogen in the tick’s fat body. High Performance Liquid Chromatography (HPLC) was employed to determine the concentration of carboxylic acids in the hemolymph and to evaluate changes in intermediary metabolic processes requiring oxygen consumption. Increases in the levels of LDH activity and lactic acid concentration indicated that fluazuron enhanced fermentative metabolism in ticks. Exposure to fluazuron was also found to increase glucose concentrations in the hemolymph over time, although no significant differences were noted daily. In addition to expanding the body of knowledge about the mode of action of fluazuron, investigations into these mechanisms may also be useful in discovering new and as yet unexplored secondary effects.

Resumo Com o objetivo de caracterizar os efeitos não-alvo da ação do fluazuron, foram realizados testes bioquímicos para analisar possíveis alterações no metabolismo de carboidratos em carrapatos Rhipicephalus (Boophilus) microplus após sua exposição ao composto. Foram coletados hemolinfa e corpo gorduroso de fêmeas ingurgitadas antes e após (4, 8 e 15 dias) a exposição ao fluazuron. Análises espectrofotométricas foram usadas para quantificar a concentração de glicose e a atividade da lactato desidrogenase (LDH) na hemolinfa e concentração de glicogênio no corpo gorduroso. Cromatografia Líquida de Alta Eficiência (CLAE) foi usada para determinação das concentrações de ácidos carboxílicos na hemolinfa e avaliar possíveis alterações em metabolismo intermediário em relação ao consumo de oxigênio. Aumento na atividade de LDH e concentração de ácido lático indicaram que o fluazuron pode regular o metabolismo fermentativo em carrapatos. A exposição ao fluazuron também aumentou a concentração de glicose na hemolinfa, apesar de não ter havido diferença significativa na comparação entre as médias no mesmo dia de avaliação. Além de aumentar o conhecimento sobre o modo de ação do fluazuron, investigações sobre tais mecanismos também são úteis no descobrimento de novos efeitos secundários ainda não explorados.

Modulatory influence of juvenile hormone analogue (JHa) and 20-hydroxyecdysone on lipophorin synthesis in red cotton bug, Dysdercus cingulatus Fabr.

Topical supply of methoprene, a juvenile hormone analogue (JHa) caused notable morphological disturbance in insects. Topical supply of methoprene to newly emerged adult female D. cingulatus caused notable disturbance and induced a dramatic reduction in the total haemolymph protein pattern and lipophorin production in tissues like fat body, ovary and haemolymph. Total protein concentration in haemolymph also showed significant reduction in 1 day old insects but increased slightly as age advanced. Application of 20-hydroxyecdysone (20-HE) to 2-day-old adult female stimulated protein synthesis intensively. Lipophorin levels in fat body and ovary also simultaneously increased. Densitometric analysis revealed that methoprene inhibits while 20-HE stimulates lipophorin production in D. cingulatus.

Effects of hypervitaminosis of vitamin B3 on silkworm biology.

A high-dose of vitamin B(3) in silkworm diet interrupts larval feeding and normal growth. High mortality of larvae occurs during molting and they cannot complete this process normally. Also the larvae exhibit nicotinamide hypervitaminosis symptoms such as immobility, dyspepsia, darkening of the skin, inability to excrete normally, exerting brownish fluid from anus and swelling of rectal muscles. Maximum larval weights in 1, 2 and 3 g/l treatments were 2.9, 1.6 and 1.2 g respectively, while maximum larval weight in the control was 5.6 g. Larval stage compared to control had increased 18, 26 and 31 days respectively. The concentration increase of uric acid in haemolymph demonstrates the hyperuricemia, while other measured biochemical compounds show significant decrease; sodium and potassium did not change significantly.

Acute and chronic effects of cadmium on blood homeostasis of an estuarine crab, Chasmagnathus granulata, and the modifying effect of salinity

Whole body oxygen consumption and some hemolymph parameters such as pH, partial pressure of gases, level of ions and lactate were measured in the estuarine crab Chasmagnathus granulata after both acute (96 h) and chronic (2 weeks) exposure to cadmium at concentrations ranging from 0.4 to 6.3 mg/l. In all instances, the crabs developed hemolymph acidosis, but no respiratory (increased PCO2) or lactate increases were evident. Hemolymph levels of sodium and calcium were always increased by cadmium exposure. The chronic toxicity of cadmium was enhanced at 12 0/00 salinity, even causing a significantly higher mortality in comparison with the higher salinity (30 0/00) used. A general metabolic arrest took place at 12 0/00 salinity in the crabs chronically exposed to cadmium, as indicated by decreases of oxygen consumption and PCO2, an increase of PO2, along with no changes in lactate levels. These imbalances were associated with severe necrosis and telangiectasia in the respiratory gills, probably leading to respiratory impairment and finally histotoxic hypoxia and death of the animals

RH-5992--an ecdysone agonist on model system of the silkworm Bombyx mori.

RH-5992 is a novel synthetic non-steroidal ecdysteroid agonist with a high selectivity towards Lepidopteran species. The effect of ecdysone agonist RH-5992 on larval period, larval weight, silk gland weight and haemolymph protein profile were examined in the model organism, the larvae of silkworm, Bombyx mori. The LD50 values were found to be 16.21 and 12.01 micrograms/larva for 72 and 96 hr respectively. In the present study, three sublethal concentrations of 1/5th, 1/10th and 1/20th of LD50 at 72 hr were selected and applied on the mid-dorsal line of the silkworm B. mori. The maximum mortality of 35% was observed in the group which received the highest (3.2 micrograms/larva) concentration of RH-5992. The mortality rate was found to be dose dependent as well as time dependent. Interesting results were observed in haemolymph profile of the RH-5992 treated larvae as staining intensity of 30 kDa protein decreased significantly whereas the effect was not marked on other major proteins like storage proteins and vitellogenin polypeptides. From the results, it is confirmed that RH-5992 causes changes in larval characters and protein profile of silkworm B. mori. It is proposed that RH-5992 may cause negative effect specifically on reproductive characters like development of ovary and egg production due to decrease in 30 kDa protein.