The feeding behaviour, activity and trappability of wild female Glossina pallidipe in relation to their pregnancy cycle

Female Glossina pallidipes Austen trapped with baited NG2B traps were subjected both to detailed ovarian dissection and to nutritional analysis. Using a calibration curve derived from dissected wild-caught, laboratory-held flies, the field females were assigned by discriminant analysis to each day of the pregnancy cycle. Field females were most available to NG2B traps while carrying the first instar larva. The nutritional characteristics of trapped field females over the pregnancy cycle lead to the following main conclusions. (i) Fat levels increase most rapidly during the egg in utero stage, while CRDW increases significantly only during the larval stages, culminating in a 4 mg increase during the last day of the third larval instar. (ii) The haematin content of the flies indicates that females feed at approximately 3-day intervals and may feed on any day of the pregnancy cycle. (iii) The estimated time of feeding during the day corresponds with the observed time of peak activity, both of which are earlier in the day later in the pregnancy cycle. (iv) The rate of fat usage reveals significantly greater flight activity on day 5 of the cycle than on other days, agreeing with the high trappability on this day, and overall females appear to use fat at twice the rate of males. Reproductive data provide a much more accurate picture of the relative sampling efficiency than do nutritional data, although the latter reveal the general trends correctly.     

Molecular Markers for Ion Compartmentation in Cells of Higher Plants

The tonoplast plays a crucial role in ion compartmentation,which is a central feature of the salt tolerance of halophytes,but we do not know the properties of the membrane that conferthis ability. A method was, therefore, developed for the isolationof vacuoles from Suaeda maritima (L.) Dum. of sufficiently highpurity to enable biochemical characterization of their lipidand protein composition. Tonoplast fractions produced by densitygradient centrifugation, as well as vacuoles isolated by a varietyof methods (including DEAE dextran lysis, digitonin lysis, andmechanical shear forces) were unacceptably contaminated. A highlypure vacuole preparation was obtained when protoplasts werelysed by a mild hypotonic shock in alkaline buffer, in the presenceof the compatible cytosolute glycine-betaine, followed by shearforce during ultracentrifugation; cytoplasmic contaminationwas prevented by the addition of the zwitterionic detergent3-([3-cholamidopropyl]dimethylammonio)-l-propanesulphonate (CHAPS).Light microscopy of this preparation revealed no intact protoplastsand no contamination by chlorophyll could be detected. Electronmicroscopy showed the vacuoles to be single-membrane-bound structures,and was the only criterion upon which vacuoles could be separatedreliably from vacuoplasts, in which the plasmalemma is collapsedon to the tonoplast. Analysis by SDS-PAGE showed that a totalof 15 polypeptides were enriched in the tonoplast and 27 inthe soluble fraction from vacuole preparations, with a patternsimilar to that reported for glycophytic species. The pure tonoplastexhibited both vanadate-insensitive ATPase and pyrophosphataseactivities, but the properties of these enzymes were broadlysimilar to those of glycophytes. Analysis of membrane fattyacids showed that the degree of saturation of the putative tonoplastpreparation increased as the assessment of the purity of thepreparation (made by microscopy) increased. The ATPase couldbe substantially purified by ion-exchange FPLC. The resultsare discussed in relation to the degree of purity needed inmembrane preparations in order to be suitable for biochemicalanalysis. Key words: ATPase, membrane lipids, tonoplast, salinity, Suaeda maritima     

Investigations on fungicides.

Uninoculated roots of pea (Pisum sativum) and French bean (Phaseolus vulgaris) have been shown to exude a number of antifungal compounds when grown in a non-sterile aqueous aerated medium. These have been identified and their possible importance in relation to disease resistance is discussed.