Polymorphism of intron-1 in the voltage-gated sodium channel gene of Anopheles gambiae s.s. populations from Cameroon with emphasis on insecticide knockdown resistance mutations

Sequence variation at the intron-1 of the voltage-gated sodium channel gene in Anopheles gambiae M- and S-forms from Cameroon was assessed to explore the number of mutational events originating knockdown resistance ( kdr ) alleles. Mosquitoes were sampled between December 2005 and June 2006 from three geographical areas: (i) Magba in the western region; (ii) Loum, Tiko, Douala, Kribi, and Campo along the Atlantic coast; and (iii) Bertoua, in the eastern continental plateau. Both 1014S and 1014F kdr alleles were found in the S-form with overall frequencies of 14% and 42% respectively. Only the 1014F allele was found in the M-form at lower frequency (11%). Analysis of a 455 bp region of intron-1 upstream the kdr locus revealed four independent mutation events originating kdr alleles, here named MS1 -1014F, S1-1014S and S2-1014S kdr- intron-1 haplotypes in S-form and MS3-1014F kdr- intron-1 haplotype in the M-form. Furthermore, there was evidence for mutual introgression of kdr 1014F allele between the two molecular forms, MS1 and MS3 being widely shared by them. Although no M/S hybrid was observed in analysed samples, this wide distribution of haplotypes MS1 and MS3 suggests inter-form hybridizing at significant level and emphasizes the rapid diffusion of the kdr alleles in Africa. The mosaic of genetic events found in Cameroon is representative of the situation in the West–Central African region and highlights the importance of evaluating the spatial and temporal evolution of kdr alleles for a better management of insecticide resistance.     

The Effects of Conditions of Growth, Extraction and Reaction on a Nucleotide Phosphatase Activity Obtained from the Shoot-Root Axes of Pisum sativum var. Alaska Seedlings

Nucleotide phosphatase activity in extracts from etiolated peaseedlings (Pisum sativum var, Alaska) was studied. A markedincrease followed rupture of the seed coat by the elongatingradicle, indicating a dependence on aerobic respiration fordevelopment of the activity. Activity from the shoot-root axiswas directly correlated with axis size, inhibition of growthresulting in a reduced activity. Growth in continuous illuminationalso reduced activity, as did imbibition of phenylalanine, tyrosine,glutathione, and sodium phosphate. The activity was greaterin the shaft regions of the axis than in the tip regions. About30 percent of the activity was associated with the nuclear—mitochondral—cellwall pellet, while the reminder was more or less evenly distributedbetween a membranee fraction of high specific activity and asoluble fraction. The effects of substractes, ions, and inhibitorson the activities of membrane and soluble fractions was quitedifferent.     

Electrochemical State of Potassium and Sodium in Free Cells of Acer pseudoplatanus

The intracellular distribution of K⁺ and Na⁺ ions has been determined by compartmental analysis of isotope exchange. The simultaneous measurement of electrical potentials allowed us to show that the distribution of K⁺ was close to thermodynamic equilibrium while the internal concentration of Na⁺ was well below the value predicted for the equilibrium. The efflux of Na⁺ was more sensitive to temperature than its influx. Both ouabain and variations in the external levels of KCl produced weak and inconsistent effects, observations which would emphasize the difference between the Na⁺ extrusion mechanism of plants and animals. The Na⁺ extrusion system of Acer cells ceased to be functional in Na⁺-depleted cells but recovered its function if the cells were placed in 10 mM NaCl, which suggests that the extrusion system was induced by the level of internal Na⁺ ions.     

DURATION OF EGG-CHAMBER GROWTH IN YOUNG IMAGINES OF DROSOPHILA MELANOGASTER MEIG

After [³H] thymidine injection to new-hatching Drosophila melanogaster females the migration of labelled egg-chambers through the ovarioles was studied by autoradiographies of the ovaries at daily intervals. The growth duration of egg-chambers which progressed during the first 48 hr was 24 hr longer than the growth duration of chambers progressing thereafter. This temporary delay of ovarian activity was related to endocrine modifications occuring in female during this s period and particularly to a JH-ecdysone interaction.     

Dependence of the Stomatal Index on Environmental Factors during Stomatal Differentiation in Leaves of Vigna sinensis L.: 1. EFFECT OF LIGHT INTENSITY

The stomatal index of the trifoliate leaves of the Cowpea isa function not only of the total radiation received but alsoof variations in radiation during the 6 d preceding the majorphase of the unfolding of the leaf lamina. Hence, for sun plantsa whole day in the shade can cause a decrease in the stomatalindex provided this day occurs during the period defined above.For shade plants it is shown that a single day of high lightintensity during this critical period will cause an increasein the stomatal index. The latter is thus a characteristic foreach individual leaf. It is postulated that the site of photoperceptioncontrolling the stomatal index is located in the expanded adultleaves. Excision and transfer of still unfolding leaves to aculture medium partially prevents the influence of the olderexpanded leaves on the stomatal index of the excised leaf.     

A geometric morphometric assessment of the effects of environment and cladogenesis on the evolution of the turtle shell

In the largest group of extant turtles, the Testudinoidea, the acquisition of an aquatic or terrestrial way of life has occurred within two clades, allowing the study of homoplasy linked to environment (commonly named convergence). Here we appraise the respective importance of two sources of morphological variation: a major cladogenetic event and a major environmental shift (aquatic vs. terrestrial). The repeatability of the same evolutionary process (environmental change) allows an assessment of the weights of both natural selection and phylogenetic constraints on several morphological features of the shell. These sources of morphological variance on the complex shell structure were studied using geometric morphometrics. We depict the morphological variation of three parts of the turtle shell: epidermal carapace, bony carapace, and plastron. In the three structures, we found that both phylogeny and environment were significant sources of morphological variation, and geometric morphometrics allowed the pattern of morphological variation due to each effect to be assessed. The assessment of the homoplasy due to environment and of the pattern of morphological variability suggests that the carapace has undergone similar morphological changes between aquatic and terrestrial environments within the two clades. The radiation of the Testudinoidea is interpreted as an adaptive radiation.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 485–501.