Additional information on an atypical population of Meloidogyne exigua Göldi, 1887 (Tylenchida: Meloidogynidae) parasitising rubber tree in Brazil

Females, males and second-stage juveniles of an unusual population of Meloidogyne exigua race 3 that only parasitises the rubber tree were examined by light and scanning electron microscopy. Previous molecular characterisation, using SCAR markers, showed consistency with other M. exigua populations from coffee. However, RAPD analysis showed high polymorphism (43.1-57.8%) but with 100% bootstrap support among populations from coffee and rubber tree. In addition, this population showed the main M. exigua esterase band (Rm: 1.5) and an additional band (Rm: 1.6) not detected in the coffee population. The morphology of this atypical population was very close to M. exigua from coffee in major diagnostic characters such as perineal pattern and male head region. However, minor differences occurred in morphological and morphometric features, particularly in the female and male stylet morphology. Cytogenetic studies confirmed the occurrence of meiotic parthenogenesis with haploid chromosome number (n = 18).

Insecticide resistance in the currant–lettuce aphid, Nasonovia ribisnigri (Hemiptera: Aphididae) in the UK

Bioassay data for a reference strain of Nasonovia ribisnigri (Mosely), exhibiting similar responses to proven susceptible strains of Myzus persicae (Sulzer) and Aphis gossypii Glover, were used to assess insecticide resistance in two suspected resistant strains and nine field strains of N. ribisnigri originating from lettuce in the UK. Results showed widespread but varied levels of resistance to pirimicarb, lower and also varied resistance to pyrethroids and organophosphates, and no significant differences in response to imidacloprid. In some strains, resistance was associated with an intensely-staining esterase band disclosed by polyacrylamide gel electrophoresis (PAGE). However, no direct relationship between esterases and resistance has yet been established. There was no biochemical evidence of an altered acetylcholinesterase contributing to pirimicarb resistance in these strains.

Biochemical and isoenzyme analyses of elephant grass, Pennisetum purpureum (Schum) varieties

This study characterized seven Pennisetum purpureum varieties, namely v. Anão, Bajra, Cameroon, Guaçu, Roxo, Taiwan A-144 and Uruckwami, through biochemical analyses, including protein, glucose and fructose contents, and polyacrylamide gel electrophoresis using the esterase system, by sampling 30, 60, 90, 120 and 150 day-old leaves. The number of nodes per stem and the percentage of bud emergence were also recorded. Variety Taiwan A-144 presented the highest number of nodes per stem and percentage of emerging buds. Protein concentration decreased gradually after 60 days for all varieties, except for Anão. Variety Guaçu presented the highest level of glucose in 90 day-old plants, whereas Cameroon presented the highest levels at 120 and 150 days. The esterase band patterns changed with plant age for all varieties, showing a tendency to increase the number of bands with time. The best age for discriminating between esterase bands of P. purpureum varieties was at 120 days, when most variation could be observed.

Changes in esterases during early embryonic development of Barytelphusa guerini (H. Milne Edwards)

Quantitative and qualitative changes in the levels of activity of esterases are studied in five stages of developing embryos of the freshwater crab Barytelphusa guerini. Esterase activity levels increase enormously as development progresses. Electrophoresis on 7.5% polyacrylamide disc gels reveals seven zones of esterase active bands. Only two of the seven zones of esterases are present in all five stages. These bands show an increase in their activity in stages III–V. Substrate specificity and inhibitor sensitivity of the enzymes were used to classify esterases. The twofold serial dilution technique was employed to estimate the relative proportion of each esterase band observed during electrophoresis. Heat denaturation studies indicate an increase in the thermal stability of the enzyme as development progresses.

Varying electrophoretic mobility of an esterase caused by a factor in extracts of Bacillus stearothermophilus cells

The esterase pattern on polyacrylamide gel of extracts from Bacillus stearothermophilus grown at different temperatures from 45 to 71 °C was examined by slab gel electrophoresis. The esterase pattern showed the presence of eight esterase bands in the extracts from bacterial cells grown at 60 °C. These bands could be divided into two groups. One group included seven esterase bands which showed constant electrophoretic mobilities at different growth temperatures. The other group included one esterase band, Est-b, which showed different mobilities depending on growth temperature. A factor, which increased the mobility of Est-b, could be separated from cell extracts by gel filtration. The mobility of partially purified Est-b was regulated by addition of various amounts of the factor. At 70 °C, the thermostability of partially purified Est-b was increased by adding the factor; this was accompanied by competitive inhibition of the enzyme activity.