CYTO-TAXONOMIC NOTES ON BUDDLEIA

Moore R. J. (Can. Dept. Agric, Plant Res. Inst., Ottawa, Ont.) Cyto-taxonomic notes on Buddleia. Amer. Jour. Bot. 47(6): 511–517. 1960.—Chromosome numbers of 29 taxa of Buddleia are reported; those of the following species are reported for the first time: B. crispa 2n=38, B. delavayi 2n=ca. 114, B. grandiflora 2n=38, B. nivea var. yunnanensis 2n=ca. 228, B. paniculata 2n=38, B. pterocaulis, 2n=ca. 228, and the artificial hybrids B. globosa × B. davidii 2n=76, B. caryopteridifolia × B. alternifolia 2n=38, Nicodemia madagascariensis × B. asiatica 2n=38. Notes on the taxonomy and nomenclature of the species are included. The evolution of the Buddleia inflorescence is briefly discussed and some natural species groups within the Asiatic species are suggested.     

Oscillations in a collapsed-tube analog of the brachial artery under a sphygmomanometer cuff

To determine whether self-excited oscillations in a Starling resistor are relevant to physiological situations, a collapsible tube conveying an aqueous flow was externally pressurized along only a central segment of its unsupported length. This was achieved by passing the tube through a shorter and wider collapsible sleeve which was mounted in Starling resistor fashion in a pressure chamber. The tube size and material, and all other experimental parameters, were as used in our previous Starling resistor studies. Both low- and high-frequency self-excited oscillations were observed, but the low-frequency oscillations were sensitive to the sleeve type and length relative to unsupported distance. Pressure-flow characteristics showed multiple oscillatory modes, which differed quantitatively from those observed in comparable Starling resistors. Slow variation of driving pressure gave differing behavior according to whether the pressure was rising or falling, in accord with the hysteresis noted on the characteristics and in the tube law. The results are discussed in terms of the various possible mechanisms of collapsible tube instability, and reasons are presented for the absence of the low-frequency mode under most physiological circumstances.     

Evolution of insecticide resistance in Culex pipiens populations: The Corsican paradox

Culex pipiens mosquitoes from Corsica have been subject to insecticide treatments since 1971, using temephos (an organophosphate). After 17 years, resistance has not developed beyond a 14-fold level. This relatively low resistance is due to the presence of several identified resistance genes, including the insensitive target ( Ace^R ) and overproduced esterases (A1, A4 and B4). The fact that only a low resistance has developed after 17 years of treatment and that this low resistance level is the result of a relatively large number of resistance genes constitute a paradox. To understand this situation and explain why a higher temephos resistance level has not evolved in Corsica as in other parts of the world, it is proposed that the occurrence (through mutation or migration) of efficient resistance genes was a limiting step, and that the only resistance genes available at that time through migration from the surrounding Mediterranean countries had a low cross-resistance to temephos. The local situation of Corsica is discussed in the light of recent data on the world distribution of the known organophosphate resistance genes in this species, and the relative role of mutation and migration in the evolution of insecticide resistance in natural populations.