The Journal of Middle East and North Africa Sciences

1-4

Authors: Ahmed Tabbabi; Ali Lamari; Hassen Ben Cheikh

Development of resistance to chlorpyrifos in Culex pipiens population from Tunisia under temephos selection pressures was investigated. The objective of this study was to follow the evolution of resistance responses in Culex pipiens larvae under laboratory conditions. The selection to temephos caused a significant increase of resistance to chlorpyrifos levels. Indeed, the LD50 resistance rate increased from 75.90 in the natural population to approximately 6620.66 in the 4th generation of selection. This resistance dropped sharply in the 5th generation (1686.35) to increase again in the last generation of selection reaching 3929.36. The reason for this unstable variation is unknown and effects related to uncontrolled environmental parameters and/or inter-strain genetic variability is probably involved. Our results showed the involvement of insensitive acetylcholinesterase (AChE), which is a common target for temephos and chlorpyrifos insecticides, in the recorded resistance. The potential to develop resistance to the chlorpyrifos is very clear in this species.

10-15

Authors: Ahmed Tabbabi; Hassen Ben Cheikh

The fitness cost associated with resistance genes was investigated on mosquito’s viability. We studied four fitness parameters in a laboratory-selected strain of Culex pipiens associated with resistance to the insecticide temephos. S-Lab was the susceptible strain used for comparison. Two genes are involved in resistance to organophosphate (OP) insecticides: Ace-1 and Ester. After 5 generations of pressure, the temephos resistance ratio increased to 60.51 at RR95, exhibited a deficiency in the following two parameters: female fecundity (χ2=infini; dl=1; P<<0.05) and mortality rate (P<<0.05). Characterizations of resistance mechanisms indicate that resistance Ace-1 alleles coding for a modified acetylcholinesterase were associated with a higher mortality rate and lower fecundity. Several previous studies were used to compare and discuss our results.

20-23

Authors: Majedah A. Al-Homaidhi

Dental caries is an infectious, communicable and multi-factorial disease. Various factors may influence the disease process. Behavioral factors such as poor oral hygiene and the consumption of sugar-containing snacks are significant factors in caries lesion initiation. Several recent studies have suggested a connection between dental caries and parental smoking, especially with maternal smoking. Children are the most susceptible group for the effect of passive smoke because their bronchial tubes are smaller and their immune systems are less developed. They also breathe faster and thus take in more harmful chemicals per kilogram of body weight than adults. Also, it has been shown dose–response relationships between the extent of smoking by parents and the salivary or plasma Cotinine level in children, therefore, the purpose of this review is to summaries the results of various epidemiological studies, and to determine if the Environmental Tobacco Smoke (ETS) affects the development of dental caries in children